Course Guide

01-IntroductionToJavaProgrammingWithJShell

Steps

Step 00 - Getting Started with Programming
Step 01 - Introduction to Multiplication Table challenge
Step 02 - Launch JShell
Step 03 - Break Down Multiplication Table Challenge
Step 04 - Java Expression - An Introduction
Step 05 - Java Expression - Exercises
Step 06 - Java Expression - Puzzles
Step 07 - Printing output to console with Java
Step 08 - Printing output to console with Java - Exercise Statements
Step 09 - Printing output to console with Java - Exercise Solutions
Step 10 - Printing output to console with Java - Puzzles
Step 11 - Advanced Printing output to console with Java
Step 12 - Advanced Printing output to console with Java - Exercises and Puzzles
Step 13 - Introduction to Variables in Java
Step 14 - Introduction to Variables in Java - Exercises and Puzzles
Step 15 - 4 Important Things to Know about Variables in Java
Step 16 - How are variables stored in memory?
Step 17 - How to name a variable?
Step 18 - Understanding Primitive Variable Types in Java
Step 19 - Understanding Primitive Variable Types in Java - Choosing a Type
Step 20 - Java Assignment Operator
Step 21 - Java Assignment Operator - Puzzles on Increment, Decrement and Compound Assignment
Step 23 - Java Conditionals and If Statement - Introduction
Step 24 - Java Conditionals and If Statement - Exercise Statements
Step 25 - Java Conditionals and If Statement - Exercise Solutions
Step 26 - Java Conditionals and If Statement - Puzzles
Step 27 - Java For Loop to Print Multiplication Table - Introduction
Step 28 - Java For Loop to Print Multiplication Table - Exercise Statements
Step 29 - Java For Loop to Print Multiplication Table - Exercise Solutions
Step 30 - Java For Loop to Print Multiplication Table - Puzzles
Step 31 - Programming Tips : JShell - Shortcuts, Multiple Lines and Variables TODO Move up
Step 32 - Getting Started with Programming - Revise all Terminology

Exercises

Expressions

Write a Java expression to calculate the number of minutes in a day.
Write a Java expression to calculate the number of seconds in a day.

Printing Output to Console

Print Hello World onto the console.
Print 5 * 3, as is.
Print the calculated value of 5 * 3.
How do we now approach the Multiplication Table print problem, for the number 5?
Print the number of seconds in a day, using the System.out.println method.
Do a syntax revision for the code that you write for each of the above exercises. In your code, identify the following elements:
- Numeric and string literals
- Expressions
- Operators
- Operands
- Method calls

Advanced Printing Output to Console

Print the following output by passing 4 values 5, ,6, 7 and sum of the numbers: 5 + 6 + 7 = 18

Variables

Create three integer variables a, b and c.
- Write a statement to print the sum of these three variables.
- Change the value of a, and then print this sum.
- Then again, change the value of b and print this sum.

If Statement

Create four integer variables a, b, c and d. - Write an if statement to print if the sum of a and b is greater than the sum of c and d.
Store three numerical values as proposed angles of a triangle in integer variables angle1, angle2 and angle3. Create an if statement to state whether these three angles together can form a triangle. Hint: A triangle is a closed geometric figure with three angles, whose sum must exactly equal 180 degrees.
Have a variable store an integer. Create an if statement to find out if it's an even number.Hint: Use operator %.

For Loop

Repeat the entire process at arriving at the Multiplication Table Print problem, now for the number 7. Start with fresh JShell session, if you're still using an existing one for quite some time (Rinse, and repeat!).
Use the final solution to print Multiplication Tables for 6 and 10.
Print the integers from 1 to 10.
Print the integers from 10 to 1.
Print the squares of the integers from 1 to 10.
Print the squares of the first 10 even integers.
Print the squares of the first 10 odd integers.

Code Snippets

3*4
System.out.println(3*4)
System.out.println("5 * 2 = 10")
3.0/2
System.out.println("5 * 2")
System.out.println(5 * 2)
System.out.println("Hello World")
System.out.println(5*3)
System.out.println("5 * 3")
System.out.println(5*3)
System.out.println("5 * 1 = 5")
System.out.println("5 * 2 = 5")
System.out.println("5 * 3 = 5")
System.out.println("24 * 60 * 60")
System.out.println(24 * 60 * 60)
System.out.println("Hello World")
System.out.println("Hello     World")
System.out.println(24   *    60    *    60)
System.out.println("Hello World")
System.out.println("HelloWorld")
System.out.println("hello world")
System.out.println("hello \"world")
System.out.println("hello \"world")
System.out.println("hello n world")
System.out.println("hello \n world")
System.out.println("hello \nworld")
System.out.println("hello\nworld")
System.out.println("hello\tworld")
System.out.println("hello \\ world")
System.out.println("hello \\\\ world")
Math.random()
System.out.println("hello \n world")
Math.min(23,45)
Math.min(23,4)
Math.max(23,4)
System.out.println("5 * 2 = 5")
System.out.println("5 * 2 = 10")
5*2
System.out.printf("5 * 2 = 10")
System.out.printf("5 * 2 = 10").println()
System.out.printf("5 * 2 = 10 %d", 5*2).println()
System.out.printf("5 * 2 = %d", 5*2).println()
System.out.printf("%d %d %d", 5, 7, 5 * 7).println()
System.out.printf("%d * %d = %d", 5, 7, 5 * 7).println()
System.out.printf("%d + %d + %d = %d", 5, 6, 7, 5 + 6 + 7).println()
System.out.printf("%d + %d + %d = %d", 5, 6, 7).println()
System.out.printf("%d + %d + %d", 5, 6, 7).println()
System.out.printf("%d + %d + %d", 5, 6).println()
System.out.printf("%d + %d + %d", 5, 6, 7, 8).println()
System.out.printf("Print %s", "Testing").println()
System.out.printf("%d + %d + %d", 5.5, 6.5, 7.5).println()
System.out.printf("%f + %f + %f", 5.5, 6.5, 7.5).println()
System.out.printf("5 * 2 = 10")
System.out.printf("%d * %d = %d", 5, 2, 5 * 2).println()
System.out.println("5 * 2 = 10")
System.out.printf("%d * %d = %d", 5, 2, 5 * 2).println()
System.out.printf("%d * %d = %d", 5, 1, 5 * 1).println()
System.out.printf("%d * %d = %d", 5, 2, 5 * 2).println()
System.out.printf("%d * %d = %d", 5, 3, 5 * 3).println()
System.out.printf("%d * %d = %d", 5, 4, 5 * 4).println()
number = 11
number
number = 12
number
number2 = 100
System.out.printf("%d * %d = %d", 5, 4, 5 * 4).println()
System.out.printf("%d * %d = %d", 5, i, 5 * i).println()
i
5 * i
i = 2
System.out.printf("%d * %d = %d", 5, i, 5 * i).println()
i = 3
System.out.printf("%d * %d = %d", 5, i, 5 * i).println()
i = 10
System.out.printf("%d * %d = %d", 5, i, 5 * i).println()
System.out.printf("a + b + c = a+b+c").println()
System.out.printf("%d + %d + %d = %d", a, b, c ,a+b+c).println()
a = 50
System.out.printf("%d + %d + %d = %d", a, b, c ,a+b+c).println()
b = 60
System.out.printf("%d + %d + %d = %d", a, b, c ,a+b+c).println()
int newVariable;
newVariable
int undeclaredVariable;
undeclaredVariable
5 * undeclaredVariable
a = 100
a = c
int noOfGoals;
int NoOfGoals;
int score;
short s;
float f = 4.0f;
float f2 = 4.5f;
double dbl = 4.5;
i = j
i
j
i = j
i = j * 2
i = i * 2
i = i + i
i = i - i
i = i - 1
i++
i
i++
i
i--
number = number + 1
number++
number--
++number
--number
number--
number
i = i + 2
i += 2
i -= 1
i *= 5
i
i /= 4
i %= 2
;
long l = 6_000_000_000l;
short numberOfGoals;
numberOfGoals++
numberOfGoals
numberOfGoals++
numberOfGoals
long populationOfTheWorld;
double average;
char ch = 'A';
ch = 'B'
char grade = 'C';
grade = 'A'
grade
boolean isEven;
isEven = true
boolean isPrime;
boolean isItRainingToday;
boolean areYouEnjoyingTheCourse;
areYouEnjoyingTheCourse = true
System.out.printf("%d * %d = %d", 5, i, 5*i);
System.out.printf("%d * %d = %d", 5, i, 5*i).println()
System.out.printf("%d * %d = %d", 5, i, 5*i).println()
System.out.printf("%d * %d = %d", 5, i, 5*i).println()
i = 7
System.out.printf("%d * %d = %d", 5, i, 5*i).println()
i = 10
i < 5
i > 5
i <= 5
i <= 10
i >= 10
System.out.println("i is less than 5");
i
if (i<5)
   System.out.println("i is less than 5");
i
i = 4
if (i<5)
   System.out.println("i is less than 5");
int number1 = 5;
int number2 = 7;
if (number2>number1)
System.out.println("number2 is greater than number1");
number2 = 3
if (number2>number1)
System.out.println("number2 is greater than number1");
int a = 1;
int b = 2;
int c = 3;
int d = 1;
if(a+b > c +d)
System.out.println("a+b is greater than c+d");
a = 6
if(a+b > c +d)
System.out.println("a+b is greater than c+d");
if ( a + b > c + d )
    System.out.println("a+b is greater than c+d");
int angle1 = 20;
int angle2 = 60;
int angle3 = 50;
if(angle1 + angle2 + angle3 == 180)
    System.out.println("Valid Triangle");
angle3 += 50
angle3
angle1
angle2
if(angle1 + angle2 + angle3 == 180)
    System.out.println("Valid Triangle");
int number = 10;
number % 2
9 % 2
8 % 2
if (number % 2 == 0)
System.out.println("number is even");
if (number % 2 == 0)
System.out.println("number is even");
number = 9
if (number % 2 == 0)
System.out.println("number is even");
i > 5
i = 5
i == 5
i == 6
if(i==5)
System.out.println("i is odd");
if(i==5)
System.out.println("i is odd");
 System.out.println("i is prime");
i == 6
i = 6
if(i==5)
System.out.println("i is odd");
 System.out.println("i is prime");
if(i==5) {
System.out.println("i is odd");
System.out.println("i is prime");
}
if(i==5) {
System.out.println("i is prime");
}
System.out.printf("%d * %d = %d", 5, i, 5*i).println()
System.out.printf("%d * %d = %d", 5, i, 5*i).println()
i = i + 1
System.out.printf("%d * %d = %d", 5, i, 5*i).println()
i = i + 1
System.out.printf("%d * %d = %d", 5, i, 5*i).println()
for( i =1; i<=10; i++) {
   System.out.printf("%d * %d = %d", 5, i, 5*i).println();
}
for( i =1; i<=10; i++) {
   System.out.printf("%d * %d = %d", 6, i, 6*i).println();
}
for( i =1; i<=10; i++) {
   System.out.printf("%d * %d = %d", 7, i, 7*i).println();
}
int table = 7;
for( i =1; i<=10; i++) {
   System.out.printf("%d * %d = %d", table, i, table*i).println();
}
table = 8
for( i =1; i<=10; i++) {
   System.out.printf("%d * %d = %d", table, i, table*i).println();
}
table = 8
for( i =1; i<=10; i++) {
   System.out.printf("%d * %d = %d", table, i, table*i).println();
}
table = 9
for( i =1; i<=10; i++) {
   System.out.printf("%d * %d = %d", table, i, table*i).println();
}
for(i =1; i<=10; i++) {
   System.out.printf("%d", i).println();
}
for(i=10; i<=1  ;i--) {
   System.out.printf("%d", i).println();
}
for(i=10; i>=1  ;i--) {
   System.out.printf("%d", i).println();
}
for(i=10; i>=1  ;i = i - 2) {
   System.out.printf("%d", i).println();
}
for(i=9; i>=1  ;i = i - 2) {
   System.out.printf("%d", i).println();
}
for(i =1; i<=10; i++) {
   System.out.printf("%d", i * i).println();
}
for(i =2; i<=10; i = i + 2) {
   System.out.printf("%d", i * i).println();
}
for(i =2; i<=20; i = i + 2) {
   System.out.printf("%d", i * i).println();
}
for(i =1; i<=10; i++) {
   System.out.printf("%d", (2 * i) * (2 * i) ).println();
}
for(i =1; i<=20; i = i + 2) {
   System.out.printf("%d", i * i).println();
}
int i = 1;
for ( ;i<=10 ;i++ );
i
for (i=1 ;i<=10 ;i++ );
int j;
for (i=1, j=2 ;i<=10 ;i++, j++ );
i
j
for (i=1, j=2 ;i<=10 ;i++, j--);
i
j
for(;;);
for(int i=1; i<=10; i++) {
System.out.println("No 1");
System.out.println("No 2");
}
for(int i=1; i<=10; i++) {
System.out.println("No 1");
System.out.println("No 2");
}
   System.out.println("i is less than 5");

02-IntroductionToMethods-MultiplicationTable

Steps

Step 00 - Section 02 - Methods - An Introduction
Step 01 - Your First Java Method - Hello World Twice and Exercise Statements
Step 02 - Introduction to Java Methods - Exercises and Puzzles
Step 03 - Programming Tip - Editing Methods with JShell
Step 04 - Introduction to Java Methods - Arguments and Parameters
Step 05 - Introduction to Java Method Arguments - Exercises
Step 06 - Introduction to Java Method Arguments - Puzzles and Tips
Step 07 - Getting back to Multiplication Table - Creating a method
Step 08 - Print Multiplication Table with a Parameter and Method Overloading
Step 09 - Passing Multiple Parameters to a Java Method
Step 10 - Returning from a Java Method - An Introduction
Step 11 - Returning from a Java Method - Exercises
Step 99 - Methods - Section Review

Exercises

Methods - Basics

Write and execute a method named sayHelloWorldThrice to print Hello World thrice.
Write and execute a method that prints the following four statements:
- I've created my first variable
- I've created my first loop
- I've created my first method
- I'm excited to learn Java

Method Parameters

Write a method printNumbers(int n) that prints all successive integers from 1 to n.
Write a method printSquaresOfNumbers(int n) that prints the squares of all successive integers from 1 to n.

Return value from Methods

Write a method that returns the sum of three integers.
Write a method that takes as input two integers representing two angles of a triangle, and computes the third angle. Hint: The sum of the three angles of a triangle is 180 degrees.

Code Snippets

3 * 4
$2
$2 * 3
for( i =1; i<=10; i++) {
System.out.printf("%d * %d = %d", table, i, table*i).println();
}
for( i =1; i<=10; i++) {
    System.out.printf("%d * %d = %d", table, i, table*i).println();
}
for( i =1; i<=10; i++) {
    System.out.printf("%d * %d = %d", table, i, table*i).println();
}
for( i =1; i<=10; i++) {
   System.out.printf("%d * %d = %d", table, i, table*i).println();
}
int table = 7;
for( i =1; i<=10; i++) {
System.out.printf("%d * %d = %d", table, i, table*i).println();
}
table = 8
for( i =1; i<=10; i++) {
System.out.printf("%d * %d = %d", table, i, table*i).println();
}
System.out.println("Hello World")
System.out.println("Hello World")
System.out.println("Hello World")
System.out.println("Hello World");
 System.out.println("Hello World");
System.out.println("Hello World");
 System.out.println("Hello World");
sayHelloWorldTwice()
sayHelloWorldTwice()
void sayHelloWorldThrice(){
 System.out.println("Hello World");
 System.out.println("Hello World");
 System.out.println("Hello World");
}
sayHelloWorldThrice()
printLearningExperience()
printLearningExperience()
void NameOfMethod(){
}
void nameOfMethod(){
}
void sayHelloWorldTwice(){
   System.out.println("HelloWorld");
   System.out.println("HelloWorld");
}
sayHelloWorldTwice()
void printLearningExperience() {
System.out.println("I've created sdf first variable");
System.out.println("I've created fsadjf first method");
System.out.println("I've created fsajdfl first loop");
System.out.println("I'm excited fasdflkjfskfsd learn Java");
}
printLearningExperience()
sayHelloWorldThrice()
sayHelloWorldTwice()
sayHelloWorld(1)
sayHelloWorld(1)
sayHelloWorld(2)
sayHelloWorld(2)
sayHelloWorld(4)
sayHelloWorld(6)
void sayHelloWorld(int noOfTimes) {
	for(int i=1; i<=noOfTimes; i++) {
		System.out.println("Hello World");
	}
}
sayHelloWorld(6)
sayHelloWorld(3)
sayHelloWorld(2)
void printNumbers(int n) {
    for(int i=1; i<=n; i++) {
	    System.out.println(i);
    }
}
printNumbers(10)
printNumbers(3)
void printSquaresOfNumbers(int n) {
    for(int i=1; i<=n; i++) {
         System.out.println(i*i);
    }
}
printSquaresOfNumbers(5)
printSquaresOfNumbers(3)
sayHelloWorld(4)
for( i =1; i<=10; i++) {
	System.out.printf("%d * %d = %d", table, i, table*i).println();
}
int i;
for(i=1;i<=10;i++)
    System.out.printf("%d * %d = %d", 5, i, 5 * i).println();
for(i=1;i<=10;i++) {
    System.out.printf("%d * %d = %d", 5, i, 5 * i).println();
}
void printMultiplicationTable() {
	for(int i=1;i<=10;i++) {
		System.out.printf("%d * %d = %d", 5, i, 5 * i).println();
	}
}
printMultiplicationTable()

void printMultiplicationTable(int table) {
	for(int i=1;i<=10;i++) {
		System.out.printf("%d * %d = %d", table, i, table * i).println();
	}
}

printMultiplicationTable(6)
printMultiplicationTable(7)
printMultiplicationTable()
printMultiplicationTable(6)
Math.max(1,2)
void sum(int firstNumber,int secondNumber) {
     int sum = firstNumber + secondNumber;
     System.out.println(sum);
}
sum(5, 10)
void sum(int firstNumber,int secondNumber, int thirdNumber) {
     int sum = firstNumber + secondNumber + thirdNumber;
     System.out.println(sum);
}
sum(5, 10, 15)
Math.max(4,5)
$110
int max = Math.max(15, 25);
max
sum(1, 10)
int sumOfTwoNumbers(int firstNumber, int secondNumber) {
    int sum = firstNumber + secondNumber;
    return sum;
}
sumOfTwoNumbers(1,1)
int sum = sumOfThreeNumbers(2,3,4);
calculateThirdAngle(20, 50)
int sumOfThreeNumbers(int firstNumber, int secondNumber, int thirdNumber) {
      int sum = firstNumber + secondNumber + thirdNumber;
      return sum;
}
sumOfThreeNumbers(1,2,3)
sumOfThreeNumbers(15,2,3)
int calculateThirdAngle(int angle1, int angle2) {
       int angle3 = 180 - (angle1 + angle2);
       return angle3;
}
calculateThirdAngle(20, 20)
calculateThirdAngle(20, 20)

03-IntroductionToJavaPlatform

Steps

Step 00 - Section 03 - Overview Of Java Platform - Section Overview
Step 01 - Overview Of Java Platform - An Introduction - java, javac, bytecode and JVM
Step 02 - Java Class and Object - First Look
Step 03 - Create a method in a Java class
Step 04 - Create and Compile Planet.java class
Step 05 - Run Planet calss with Java - Using a main method
Step 06 - Play and Learn with Planet Class
Step 07 - JDK vs JRE vs JVM

Code Snippets (Including Output)

jshell> System.out.println("I love JShell");
I love JShell

jshell> class Country {
   ...> }
|  created class Country

jshell> Country india = new Country()
india ==> Country@6e06451e

jshell> Country usa = new Country()
usa ==> Country@6e1567f1

jshell> class Planet {
   ...> }
|  created class Planet

jshell> Planet planet = new Planet()
planet ==> Planet@56ef9176

jshell> Planet earth = new Planet()
earth ==> Planet@1ed4004b

jshell> Planet venus = new Planet()
venus ==> Planet@25bbe1b6

jshell> void printMultiplicationTable() {
   ...>     for(int i=1;i<=10;i++) {
   ...>         System.out.printf("%d * %d = %d", 5, i, 5 * i).println();
   ...>     }
   ...> }
|  created method printMultiplicationTable()

jshell> void printMultiplicationTable(int table) {
   ...>     for(int i=1;i<=10;i++) {
   ...>         System.out.printf("%d * %d = %d", table, i, table * i).println();
   ...>     }
   ...> }
|  created method printMultiplicationTable(int)

jshell> 
 
jshell> /methods
|    void |    void printMultiplicationTable()
|    void printMultiplicationTable(int)

jshell>  
jshell> class Planet {
   ...> }
|  modified class Planet

jshell> Planet earth = new Planet()
earth ==> Planet@73846619

jshell> Planet venus = new Planet()
venus ==> Planet@4bec1f0c

jshell> class Planet {
   ...>      void revolve() {
   ...>           System.out.println("Revolve");
   ...>      }
   ...> }
|  replaced class Planet
|    update replaced variable planet, reset to null
|    update replaced variable earth, reset to null
|    update replaced variable venus, reset to null

jshell> Planet earth = new Planet()
earth ==> Planet@192b07fd

jshell> Planet venus = new Planet()
venus ==> Planet@64bfbc86

jshell> Planet.revolve()
|  Error:
|  non-static method revolve() cannot be referenced from a static context
|  Planet.revolve()
|  ^------------^

jshell> earth.revolve()
Revolve

jshell> venus.revolve()
Revolve

jshell> class Country {
   ...>    void comingSoon() {
   ...>       System.out.println("Coming Soon");
   ...>    }
   ...> }
|  replaced class Country
|    update replaced variable country, reset to null
|    update replaced variable india, reset to null
|    update replaced variable usa, reset to null

jshell> Country india = new Country()
india ==> Country@60c6f5b

jshell> Country netherlands = new Country()
netherlands ==> Country@3c0f93f1

jshell> india.comingSoon()
Coming Soon

jshell> netherlands.comingSoon()
Coming Soon

jshell> /list Country

  27 : class Country {
          void comingSoon() {
             System.out.println("Coming Soon");
          }
       }

jshell> /list Planet

  22 : class Planet {
            void revolve() {
                 System.out.println("Revolve");
            }
       }

jshell>

/03-IntroductionToJavaPlatform/Planet.java

class Planet {

    void revolve() {
         System.out.println("Revolve");
    }

    public static void main(String[] args) {
    	Planet earth = new Planet();
    	earth.revolve();
    }
}

04-IntroductionToEclipse-FirstJavaProject

Steps

Step 00 - Intro to Section and Installing Eclipse
Step 01 - Creating a New Java Project with Eclipse
Step 02 - Your first Java class with Eclipse
Step 03 - Writing Multiplication Table Java Program with Eclipse
Step 04 - Adding more methods for Multiplication Table Program
Step 05 - Programming Tip 1 : Refactoring with Eclipse
Step 06 - Programming Tip 2 : Debugging with Eclipse
Step 07 - Programming Tip 3 : Eclipse vs JShell - How to choose?

Code Examples

/04-IntroductionToEclipse-FirstJavaProject/src/com/in28minutes/firstjavaproject/HelloWorld.java

package com.in28minutes.firstjavaproject;

public class HelloWorld {

	public static void main(String[] args) {
		
	}

}

/04-IntroductionToEclipse-FirstJavaProject/src/com/in28minutes/firstjavaproject/KeyboardShortcuts.java

package com.in28minutes.firstjavaproject;

public class KeyboardShortcuts {
	public static void main(String[] args) {
		int i = 0;
		System.out.println(i);
	}
}

/04-IntroductionToEclipse-FirstJavaProject/src/com/in28minutes/firstjavaproject/MultiplicationTable.java

package com.in28minutes.firstjavaproject;

public class MultiplicationTable {
	
	void print() {
		print(5);
	}
	
	void print(int table) {
		print(table, 1, 10);
	}
	
	void print(int table, int from, int to) {
		for (int i = from; i <= to; i++) {
			System.out.printf("%d X %d = %d", table, i, table * i).println();
		}
	}
}

/04-IntroductionToEclipse-FirstJavaProject/src/com/in28minutes/firstjavaproject/MultiplicationTableRunner.java

package com.in28minutes.firstjavaproject;

public class MultiplicationTableRunner {

	public static void main(String[] args) {
		MultiplicationTable table = new MultiplicationTable();
		table.print();
		
		//table.print(6);
		//table.print(6, 11, 20);
	}

}

/04-IntroductionToEclipse-FirstJavaProject/src/com/in28minutes/firstjavaproject/MutliplicationTableBeforeRefactoring.java

package com.in28minutes.firstjavaproject;

public class MutliplicationTableBeforeRefactoring {
	void print() {
		for (int i = 1; i <= 10; i++) {
			System.out.printf("%d X %d = %d", 5, i, 5 * i).println();
		}
	}

	void print(int table) {
		for (int i = 1; i <= 10; i++) {
			System.out.printf("%d X %d = %d", table, i, table * i).println();
		}
	}

	void print(int table, int from, int to) {
		for (int i = from; i <= to; i++) {
			System.out.printf("%d X %d = %d", table, i, table * i).println();
		}
	}
}

05-IntroductionToObjectOrientedProgramming

Steps

Step 00 - Introduction to Object Oriented Programming - Section Overview
Step 01 - Introduction to Object Oriented Programming - Basics
Step 02 - Introduction to Object Oriented Programming - Terminology - Class, Object, State and Behavior
Step 03 - Introduction to Object Oriented Programming - Exercise - Online Shopping System and Person
Step 04 - Create Motor Bike Java Class and a couple of objects
Step 05 - Exercise Solutions - Book class and Three instances
Step 06 - Introducing State of an object with speed variable
Step 07 - Understanding basics of Encapsulation with Setter methods
Step 08 - Exercises and Tips - Getters and Generating Getters and Setters with Eclipse
Step 09 - Puzzles on this and initialization of member variables
Step 10 - First Advantage of Encapsulation
Step 11 - Introduction to Encapsulation - Level 2
Step 12 - Encapsulation Exercises - Better Validation and Book class
Step 13 - Introdcution to Abstraction
Step 14 - Introduction to Java Constructors
Step 15 - Introduction to Java Constructors - Exercises and Puzzles
Step 16 - Introduction to Object Oriented Programming - Conclusion

Exercises

In each of the following systems, identify the basic entities involved, and organize them using object oriented terminology:
- Online Shopping System
- Person
Provide Better Encapsulation and Validation for Book and MotorBike class
Create a constructor for Book class and create three instances

Code Examples

/05-IntroductionToObjectOrientedProgramming/src/com/in28minutes/oops/Book.java

package com.in28minutes.oops;

public class Book {
	
	private int noOfCopies;

	public Book(int noOfCopies) {
		this.noOfCopies = noOfCopies;
	}

	public void setNoOfCopies(int noOfCopies) {
		if (noOfCopies > 0)
			this.noOfCopies = noOfCopies;
	}

	public void increaseNoOfCopies(int howMuch) {
		setNoOfCopies(this.noOfCopies + howMuch);
	}

	public void decreaseNoOfCopies(int howMuch) {
		setNoOfCopies(this.noOfCopies - howMuch);
	}

}

/05-IntroductionToObjectOrientedProgramming/src/com/in28minutes/oops/BookRunner.java

package com.in28minutes.oops;

public class BookRunner {

	public static void main(String[] args) {
		// Create a new class called Book 
		// Create three instances
		Book artOfComputerProgramming = new Book(100);
		Book effectiveJava = new Book(50);
		Book cleanCode = new Book(40);
		
		artOfComputerProgramming.setNoOfCopies(100);
		effectiveJava.setNoOfCopies(50);
		cleanCode.setNoOfCopies(45);
	}

}

/05-IntroductionToObjectOrientedProgramming/src/com/in28minutes/oops/MotorBike.java

package com.in28minutes.oops;

public class MotorBike {
	//state
	private int speed; //member variable
	

	//constructors
	MotorBike() {
		this(5);
	}
	
	MotorBike(int speed) {
		this.speed = speed;
	}
	
	//behavior
	public int getSpeed() {
		return speed;
	}

	public void setSpeed(int speed) {
		if(speed > 0 )
			this.speed = speed;
	}

	public void increaseSpeed(int howMuch) {
		setSpeed(this.speed + howMuch);
	}

	public void decreaseSpeed(int howMuch) {
		setSpeed(this.speed - howMuch);
	}
	
	void start() {
		System.out.println("Bike Started");
	}
}

/05-IntroductionToObjectOrientedProgramming/src/com/in28minutes/oops/MotorBikeRunner.java

package com.in28minutes.oops;

public class MotorBikeRunner {

	public static void main(String[] args) {
		
		MotorBike ducati = new MotorBike(100);
		
		MotorBike honda = new MotorBike(200);
		
		MotorBike somethingElse = new MotorBike();
		
		System.out.println(ducati.getSpeed());
		
		System.out.println(honda.getSpeed());
		
		System.out.println(somethingElse.getSpeed());

		
		ducati.start();

		honda.start();
		
		//ducati.setSpeed(100);
		
		ducati.increaseSpeed(100);
				
		honda.increaseSpeed(100);
		
		ducati.decreaseSpeed(250);
		
		honda.decreaseSpeed(250);
		
		System.out.println(ducati.getSpeed());
		
		System.out.println(honda.getSpeed());
	}

}

// Create a new class called Book 
// Create three instances
// Art Of Computer Programming
// Effective Java
// Clean Code

/05-IntroductionToObjectOrientedProgramming/entireoutput-constructor-puzzles.txt

Last login: Mon Jan 29 10:33:44 on ttys000
Rangas-MacBook-Pro:~ rangaraokaranam$ jshell
|  Welcome to JShell -- Version 9.0.1
|  For an introduction type: /help intro

jshell> class Cart {
   ...> };
|  created class Cart

jshell> Cart cart1 = new Cart();
cart1 ==> Cart@3f49dace

jshell> class Cart {
   ...>     Cart() {
   ...>     }
   ...> };
|  replaced class Cart
|    update replaced variable cart1, reset to null

jshell> Cart cart1 = new Cart();
cart1 ==> Cart@59494225

jshell> class Cart {
   ...>     Cart() {
   ...>         System.out.println("Constructor is called");
   ...>     }
   ...> }
|  modified class Cart

jshell> Cart cart1 = new Cart();
Constructor is called
cart1 ==> Cart@6e1567f1

jshell>

06-PrimitiveDataTypesAndAlternatives

Steps

Step 00 - Primitive Data Types in Depth - Section Overview
Step 01 - Basics about Java Integer Data Types - Casting, Operators and More
Step 02 - Java Integer Data Types - Puzzles - Octal, Hexadecimal, Post and Pre increment
Step 03 - Java Integer Data Types - Exercises - BiNumber - add, multiply and double
Step 04 - Java Floating Point Data Types - Casting , Conversion and Accuracy
Step 05 - Introduction to BigDecimal Java Class
Step 06 - BigDecimal Puzzles - Adding Integers
Step 07 - BigDecimal Exercises - Simple Interest Calculation
Step 08 - Java Boolean Data Type - Relational and Logical Operators
Step 09 - Java Boolean Data Type - Puzzles - Short Circuit Operators
Step 10 - Java Character Data Type char - Representation and Conversion
Step 11 - Java char Data Type - Exercises 1 - isVowel
Step 12 - Java char Data Type - Exercises 2 - isDigit
Step 13 - Java char Data Type - Exercises 3 - isConsonant, List Upper Case and Lower Case Characters
Step 14 - Primitive Data Types in Depth - Conclusion

Exercises

Big Decimal

Calculate formula for Simple Interest Formula
- Total Amount = principal + principal * interest * noOfYears;

 SimpleInterestCalculator calculator = 
        new SimpleInterestCalculator("4500.00", "7.5");
 BigDecimal totalValue = 
        calculator.calculateTotalValue(5);// 5 years
 System.out.println(totalSum);

char data type

Implement MyChar class

MyChar myChar = new MyChar('c');
System.out.println(myChar.isVowel());
        //'a', 'e', 'i', 'o', 'u' and Capitals
System.out.println(myChar.isDigit());
System.out.println(myChar.isAlphabet());
MyChar.printLowerCaseAlphabets();
MyChar.printUpperCaseAlphabets();

Code Examples

/06-PrimitiveDataTypesAndAlternatives/commands.txt

Byte.SIZE
Byte.BYTES
Byte.MAX_VALUE
Byte.MIN_VALUE
Short.BYTES
Integer.BYTES
Long.BYTES
Integer.MAX_VALUE
Short.MAX_VALUE
Byte.SIZE
Byte.MIN_VALUE
Byte.MAX_VALUE
Short.BYTES
Integer.BYTES
Long.BYTES
Integer.MAX_VALUE
byte c = 13;
long l = 50000000000l;
i = (int) l
l = i
int eight = 010;
int sixteen = 0x10;
int fifteen = 0XF;
int big = 0XBBAACC;
Short.MAX_VALUE
short s = (short) i;
int i1 = s;
i
i
i
i
34.5
34.56789
double dbl = 34.5678;
float f2 = (float)dbl;
dbl++
dbl--
dbl % 5
float f = i;
34.56789876 + 34.2234
number1.add(number2);
number1
BigDecimal number3 = number1.add(number2);
number1
BigDecimal number1 = new BigDecimal("34.56789876");
BigDecimal number10 = new BigDecimal(34.2234);
BigDecimal number11 = new BigDecimal("34.56789876");
number10.add(number11)
number10.multiply(number11)
BigDecimal number = new BigDecimal("11.5");
BigDecimal number2 = new BigDecimal("23.45678");
number.add(number2)
number.add(new BigDecimal(i))
number.multiply(new BigDecimal(i))
number.divide(new BigDecimal(100))
number.divide(new BigDecimal("100.01234"))
number.divide(new BigDecimal("100.012"))
number.divide(new BigDecimal("100.12"))
number.divide(new BigDecimal("100.1"))
number.divide(new BigDecimal("1001"))
number.divide(new BigDecimal("100"))
boolean isValue = false;
i > 7
i >= 7
i < 7
i <= 7
i == 6
i == 7
i == 8
i = 8
i = 7
i == 7
i > 15
i >= 15
i <= 25
i >= 15 && i <= 25
i = 30
i >= 15 && i <= 25
i = 5
i >= 15 && i <= 25
true && true
true && false
false && true
false && false
false || true
false || true
true || false
true || true
false || false
false ^ false
false ^ true
true ^ false
true ^ true
!true
!false
int x = 6;
!(x>7)
!(x>7)
true || ++i==11
i
int i = 10;
int j = 15;
j > 15 && i++ > 5
j
i
j > 15 & i++ > 5
j
i
i++;
i++;
char ch2 = '\u0022';
char ch3 = '\u00A2';
ch++
ch
++ch
++ch
ch + 5
ch
(int)ch
ch
System.out.println(ch);
char ch = '\t';
System.out.println(ch);
System.out.println(ch);
(int)'1'
(int)'0'
(int)'9'
(int)'2'
(int)'a'
(int)'z'
(int)'A'
(int)'Z'
		for (char ch = 'A'; ch <= 'Z'; ch++) {
			System.out.println(ch);

}
		for (char ch = 'A'; ch <= 'Z'; ch++) {
			System.out.println(ch);
}
		for (char ch = 'A'; ch <= 'C'; ch++) {
			System.out.println(ch);
}

/06-PrimitiveDataTypesAndAlternatives/src/com/in28minutes/primitive/datatypes/BiNumber.java

package com.in28minutes.primitive.datatypes;

public class BiNumber {
	private int number1;
	private int number2;

	public int getNumber1() {
		return number1;
	}

	public void setNumber1(int number1) {
		this.number1 = number1;
	}

	public int getNumber2() {
		return number2;
	}

	public void setNumber2(int number2) {
		this.number2 = number2;
	}

	public BiNumber(int number1, int number2) {
		this.number1 = number1;
		this.number2 = number2;
	}

	public int add() {
		return number1 + number2;
	}

	public int multiply() {
		return number1 * number2;
	}

	public void doubleValue() {
		this.number1 *= 2;
		this.number2 *= 2;
	}
}

/06-PrimitiveDataTypesAndAlternatives/src/com/in28minutes/primitive/datatypes/BiNumberRunner.java

package com.in28minutes.primitive.datatypes;

public class BiNumberRunner {

	public static void main(String[] args) {
		BiNumber numbers = new BiNumber(2, 3);
		
		System.out.println(numbers.add());//2+3
		System.out.println(numbers.multiply());//2*3
		
		numbers.doubleValue();//Double both numbers 
		
		System.out.println(numbers.getNumber1());//4
		System.out.println(numbers.getNumber2());//6
	}

}

/06-PrimitiveDataTypesAndAlternatives/src/com/in28minutes/primitive/datatypes/MyChar.java

package com.in28minutes.primitive.datatypes;

public class MyChar {

	private char ch;

	public MyChar(char ch) {
		this.ch = ch;
	}

	public boolean isVowel() {
		//'a' e i o u or A E I O U
		if(ch == 'a' || ch == 'A')
			return true;

		if(ch == 'e' || ch == 'E')
			return true;
		
		if(ch == 'i' || ch == 'E')
			return true;
		
		if(ch == 'o' || ch == 'O')
			return true;
		
		if(ch == 'u' || ch == 'U')
			return true;
		
		return false;
	}

	public boolean isDigit() {
		if(ch >= 48 && ch <=57) //between '0' and '9'  
		  return true;
		
		return false;
	}

	public boolean isAlphabet() {
		if(ch >= 97 && ch <=122) //between 'a' and 'z'  
		  return true;

		if(ch >= 65 && ch <=90) //between 'A' and 'Z'  
			  return true;

		return false;
	}

	public boolean isConsonant() {
		//Alphabet and it is not VOWEL
		//! [a , e, i ,o , u]
		if(isAlphabet() && !isVowel()) 
			return true;
		
		return false;
		
	}

	public static void printLowerCaseAlphabets() {
		//'a' to 'z'
		for (char ch = 'a'; ch <= 'z'; ch++) {
			System.out.println(ch);
		}
	}

	public static void printUpperCaseAlphabets() {
		for (char ch = 'A'; ch <= 'Z'; ch++) {
			System.out.println(ch);
		}
		
	}
}

/06-PrimitiveDataTypesAndAlternatives/src/com/in28minutes/primitive/datatypes/MyCharRunner.java

package com.in28minutes.primitive.datatypes;

public class MyCharRunner {

	public static void main(String[] args) {
		MyChar myChar = new MyChar('B');
		System.out.println(myChar.isVowel());
		
		//'a', 'e', 'i', 'o', 'u' and Capitals
		System.out.println(myChar.isDigit());
		System.out.println(myChar.isAlphabet()); //'a' to 'z' or 'A' to 'Z'

		System.out.println(myChar.isConsonant());
		
		MyChar.printLowerCaseAlphabets();
		MyChar.printUpperCaseAlphabets();
	}

}

/06-PrimitiveDataTypesAndAlternatives/src/com/in28minutes/primitive/datatypes/SimpleInterestCalculator.java

package com.in28minutes.primitive.datatypes;

import java.math.BigDecimal;

public class SimpleInterestCalculator {

	BigDecimal principal;

	BigDecimal interest;

	public SimpleInterestCalculator(String principal, String interest) {
		this.principal = new BigDecimal(principal);
		this.interest = new BigDecimal(interest).divide(new BigDecimal(100));
	}

	public BigDecimal calculateTotalValue(int noOfYears) {
		// Total Value = principal + principal * interest * noOfYears;
		BigDecimal noOfYearsBigDecimal = new BigDecimal(noOfYears);
		BigDecimal totalValue = principal.add(principal.multiply(interest).multiply(noOfYearsBigDecimal));
		return totalValue;
	}

}

/06-PrimitiveDataTypesAndAlternatives/src/com/in28minutes/primitive/datatypes/SimpleInterestCalculatorRunner.java

package com.in28minutes.primitive.datatypes;

import java.math.BigDecimal;

public class SimpleInterestCalculatorRunner {

	public static void main(String[] args) {

		SimpleInterestCalculator calculator = 
		        new SimpleInterestCalculator("4500.00", "7.5");
		 BigDecimal totalValue = 
		        calculator.calculateTotalValue(5);// 5 years
		 //6187.50000
		 System.out.println(totalValue);
	}

}

07-Conditionals

Steps

Step 00 - Conditionals with Java - Section Overview
Step 01 - Introduction to If Else Statement
Step 02 - Introduction to Nested If Else
Step 03 - If Else Statement - Puzzles
Step 04 - If Else Problem - How to get User Input in Java?
Step 05 - If Else Problem - How to get number 2 and choice from user?
Step 06 - If Else Problem - Implementing with Nested If Else
Step 07 - Java Switch Statement - An introduction
Step 08 - Java Switch Statement - Puzzles - Default, Break and Fall Through
Step 09 - Java Switch Statement - Exercises - isWeekDay, nameOfMonth, nameOfDay
Step 10 - Java Ternary Operation - An Introduction
Step 11 - Conditionals with Java - Conclusion

Exercises

If and Nested If Else - Design a Menu

Ask User for input
- Enter two numbers
- Choose an Operation
  - add
  - multiply
  - divide
  - subtract
  - ...
- Publish Result

Enter Number1: 
2

Enter Number2: 
4

1 - Add
2 - Subtract
3 - Divide
4 - Multiply
Choose Operation: 4

Result is - 8

Switch

public static boolean isWeekDay(int dayNumber) {
- input - number of day 0 (Sunday) to 6(Saturday)
- return if the day is a Week Day.
public static String determineNameOfMonth(int monthNumber) {
- input - number of month 1(January) to 12(December)
- output - Name of month
public static String determineNameOfDay(int dayNumber) {
- input - number of day 0 (Sunday) to 6(Saturday)
- Return the day of week in text

Code Examples

/07-Conditionals/commands.txt

if(true) {
   System.out.println("True");
}
if(false) {
   System.out.println("True");
}
if(i==3) {
   System.out.println("True");
}
if(i<2) {
    System.out.println("True");
}
if(i<=3 || i>=35) {
    System.out.println("True");
}
if(i<=3 && i>=35) {
    System.out.println("True");
}
if (i==3) {
   System.out.println("True");
} else {
   System.out.println("i is not 3");
}
i = 5
if (i==3) {
   System.out.println("True");
} else {
   System.out.println("i is not 3");
}
if(i==1) {
   System.out.println("i");
}
switch (i) {
   case 1 : System.out.println("1");
   case 5 : System.out.println("5");
   default : System.out.println("default");
}
i = 1
switch (i) {
   case 1 : System.out.println("1");
   case 5 : System.out.println("5");
   default : System.out.println("default");
}
switch (i) {
   case 1 : System.out.println("1"); break;
   case 5 : System.out.println("5"); break;
   default : System.out.println("default"); break;
}
boolean isEven;
int i =5;
if(i%2==0) {
  isEven = true;
} else {
  isEven = false;
}
isEven
i = 6
if(i%2==0) {
  isEven = false;
}
if(i%2==0) {
  isEven = true;
} else {
  isEven = false;
}
isEven
isEven = ( i%2==0 ? true : false  )
i = 6
isEven = ( i%2==0 ? true : false  )
i = 7
isEven = ( i%2==0 ? true : false  )
i = 6
String even = ( i%2 ==0 ? "YES" : "NO" );

/07-Conditionals/src/com/in28minutes/ifstatement/examples/IfStatementRunner.java

package com.in28minutes.ifstatement.examples;

public class IfStatementRunner {

	public static void main(String[] args) {
		puzzle5();
	}

	private static void puzzle1() {
		int k = 15;
		if (k > 20) {
			System.out.println(1);
		} else if (k > 10) {
			System.out.println(2);
		} else if (k < 20) {
			System.out.println(3);
		} else {
			System.out.println(4);
		}
		
	}

	private static void puzzle2() {
		int l = 15;

		if (l < 20)
			System.out.println("l<20");//
		if (l > 20)
			System.out.println("l>20");
		else
			System.out.println("Who am I?");//
	}

	
	
	private static void puzzle3() {
		int m = 15;

		if(m>20) 
		    if(m<20)
		System.out.println("m>20");
		    else
		System.out.println("Who am I?");
	}


	private static void puzzle5() {
		int number = 5;
		if(number < 0) 
		    number = number + 10; 
		number++; 
		System.out.println(number);
	}

	private static void basicNestedIfElse() {
		int i = 24;
		// i is 25
		// i is 24
		// i is neither 25 or 24
		if (i == 25) {
			System.out.println("i = 25");
		} else if (i == 24) {
			System.out.println("i = 24");
		} else if (i == 23) {
			System.out.println("i = 23");
		} else {
			System.out.println("i != 24 and i !=25 and i !=23");
		}
	}

}

/07-Conditionals/src/com/in28minutes/ifstatement/examples/MenuRunner.java

package com.in28minutes.ifstatement.examples;

import java.util.Scanner;

public class MenuRunner {
	public static void main(String[] args) {
		// Type obj = new Type(argument);
		Scanner scanner = new Scanner(System.in);
		System.out.print("Enter Number1: ");
		int number1 = scanner.nextInt();

		System.out.print("Enter Number2: ");
		int number2 = scanner.nextInt();

		System.out.println("Choices Available are ");
		System.out.println("1 - Add");
		System.out.println("2 - Subtract");
		System.out.println("3 - Divide");
		System.out.println("4 - Multiply");

		System.out.print("Enter Choice: ");
		int choice = scanner.nextInt();

		System.out.println("Your Choices are");
		System.out.println("Number1 " + number1);
		System.out.println("Number2 " + number2);
		System.out.println("Choice " + choice);

		performOperationUsingSwitch(number1, number2, choice);
	}

	private static void performOperationUsingNestedIfElse(int number1, int number2, int choice) {
		if (choice == 1) {
			System.out.println("Result " + (number1 + number2));
		} else if (choice == 2) {
			System.out.println("Result " + (number1 - number2));
		} else if (choice == 3) {
			System.out.println("Result " + (number1 / number2));
		} else if (choice == 4) {
			System.out.println("Result " + (number1 * number2));
		} else {
			System.out.println("Invalid Operation");
		}
	}

	private static void performOperationUsingSwitch(int number1, int number2, int choice) {
		switch (choice) {
		case 1:
			System.out.println("Result " + (number1 + number2));
			break;
		case 2:
			System.out.println("Result " + (number1 - number2));
			break;
		case 3:
			System.out.println("Result " + (number1 / number2));
			break;
		case 4:
			System.out.println("Result " + (number1 * number2));
			break;
		default:
			System.out.println("Invalid Operation");
			break;
		}

	}

}

/07-Conditionals/src/com/in28minutes/ifstatement/examples/SwitchExercisesRunner.java

package com.in28minutes.ifstatement.examples;

public class SwitchExercisesRunner {

	public static void main(String[] args) {
		System.out.println(isWeekDay(5));
	}

	public static boolean isWeekDay(int dayNumber) {
		switch(dayNumber) {
		//case 0 :
		//case 6 : return false;
		case 1 : 
		case 2 :
		case 3 :
		case 4 :
		case 5 : return true;
		}

		return false;
	}
	
	public static String determineNameOfDay(int dayNumber) {
		switch (dayNumber) {
		case 0:
			return "Sunday";
		case 1:
			return "Monday";
		case 2:
			return "Tuesday";
		case 3:
			return "Wednesday";
		case 4:
			return "Thursday";
		case 5:
			return "Friday";
		case 6:
			return "Saturday";
		}

		return "Invalid_day";
	}
}

/07-Conditionals/src/com/in28minutes/ifstatement/examples/SwitchStatementRunner.java

package com.in28minutes.ifstatement.examples;

public class SwitchStatementRunner {
	public static void main(String[] args) {
		puzzle4();
	}

	private static void puzzle1() {
		int number = 2;
		switch (number) {
		case 1:
			System.out.println(1);
		case 2:
			System.out.println(2);
		case 3:
			System.out.println(3);
		default:
			System.out.println("Default");
		}
	}

	private static void puzzle2() {
		int number = 2;
		switch (number) {
		case 1:
			System.out.println(1);
			break;
		case 2:
		case 3:
			System.out.println("Number is 2 or 3");
			break;
		default:
			System.out.println("Default");
			break;
		}
	}

	private static void puzzle3() {
		int number = 10;
		switch (number) {
		case 1:
			System.out.println(1);
			break;
		case 2:
			System.out.println(2);
			break;
		case 3:
			System.out.println(3);
			break;
		default:
			System.out.println("Default");
			break;
		}
	}

	private static void puzzle4() {
		int number = 10;
		switch (number) {
		default:
			System.out.println("Default");
			break;
		case 1:
			System.out.println(1);
			break;
		case 2:
			System.out.println(2);
			break;
		case 3:
			System.out.println(3);
			break;
		}
	}

	private static void puzzle5() {
		long l = 15;
		/*switch(l){
		
		}*/
	}

	private static void puzzle6() {
		int number = 10;
		int i = number * 2;
		switch (number) {
		 //case number>5: System.out.println("number>5");
		}
	}

}

08-Loops

Steps

Step 00 - Java Loops - Section Introduction
Step 01 - Java For Loop - Syntax and Puzzles
Step 02 - Java For Loop - Exercises Overview and First Exercise Prime Numbers
Step 03 - Java For Loop - Exercise - Sum Upto N Numbers and Sum of Divisors
Step 04 - Java For Loop - Exercise - Print a Number Triangle
Step 05 - While Loop in Java - An Introduction
Step 06 - While Loop - Exericises - Cubes and Squares upto limit
Step 07 - Do While Loop in Java - An Introduction
Step 08 - Do While Loop in Java - An Example - Cube while user enters positive numbers
Step 09 - Introduction to Break and Continue
Step 10 - Selecting Loop in Java - For vs While vs Do While

Exercises

For Loop

Implement MyNumber class with behavior shown in the example below:

MyNumber number = new MyNumber(9);

number.isPrime(); //Is a number Prime? 
//Hint : 5 => true, 7 => true, 11 => true, 6 => false

int sum = number.sumUptoN();//Sum of numbers upto n?
//1 + 2 + 3 + 4 + 5 + 6

int sumOfDivisors = number.sumOfDivisors();

number.printANumberTriangle();
//1
//1 2
//1 2 3
//1 2 3 4 
//1 2 3 4 5

While

Implement WhileNumberPlayer class with behavior shown in the example below:

WhileNumberPlayer player = new WhileNumberPlayer(30);//limit

player.printSquaresUptoLimit();
//For limit = 30, output would be 1 4 9 16 25

player.printCubesUptoLimit();
//For limit = 30, output would be 1 8 27

Choosing Loops

Thinking Exercise

What would we use for the Menu
If we would want to run the Menu again and again?

Enter Number1: 
2

Enter Number2: 
4

1 - Add
2 - Subtract
3 - Divide
4 - Multiply
5 - Exit

Choose Operation: 4
Result is 8

Choose Operation: 1
Result is 6

Choose Operation: 5

Thank You!

Code Examples

/08-Loops/commands.txt

for (int i = 0; i<= 10; i++) {
   System.out.print (i + " ");
}
for (int i = 0; i<= 10; i = i + 2) {
   System.out.print (i + " ");
}
for (int i = 1; i<= 10; i = i + 2) {
   System.out.print (i + " ");
}
for (int i = 11; i<= 10; i = i + 2) {
   System.out.print (i + " ");
}
for (int i = 11; i<= 20;) {
   System.out.print (i + " ");
   i++;
}
for (; i<= 30;i++) {
   System.out.print (i + " ");
}
9 % 2
9 % 3
if (i>2) {
   System.out.println("i>2");
}
int i = 3;
if (i>2) {
   System.out.println("i>2");
}
i = 0
while (i <5) {
   System.out.println(i);
   i++;
}
i
i = 6
while (i < 5) {
   System.out.println(i);
   i++;
}
i = -2
while (i < 5) {
   System.out.println(i);
}
while (i < 5) {
   System.out.println(i);
   i++;
}
i
while (i < 5) {
   System.out.print(i + " ");
   i++;
}
i
i = 1
do {
   System.out.print(i + " ");
   i++;
} while (i<5);
i = 10
while (i < 5) {
   System.out.print(i + " ");
   i++;
}
do {
   System.out.print(i + " ");
   i++;
} while (i<5);
for(i=1;i<=10;i++) {
   if(i==5)
      break;
   System.out.print(i + " ");
}
for(i=1;i<=10;i++) {
   if(i%2==0)
      break;
   System.out.print(i + " ");
}
for(i=1;i<=10;i++) {
   if(i%2==0)
     continue;
   System.out.print(i + " ");
}
for(i=1;i<=10;i++) {
   if(i%2!=0)
     continue;
   System.out.print(i + " ");
}

/08-Loops/src/com/in28minutes/loops/DoWhileRepeatedQuestionRunner.java

package com.in28minutes.loops;

import java.util.Scanner;

public class DoWhileRepeatedQuestionRunner {

	public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);
		int number = -1;

		do {
			if (number != -1) {
				System.out.println("Cube is " + (number * number * number));
			}
			System.out.print("Enter a number: ");
			number = scanner.nextInt();
		} while (number >= 0);
		System.out.print("Thank You! Have Fun!");
	}

}

/08-Loops/src/com/in28minutes/loops/MyNumber.java

package com.in28minutes.loops;

public class MyNumber {

	private int number;

	public MyNumber(int number) {
		this.number = number;
	}

	public boolean isPrime() {
		// 2 to number-1
		// How can check if a number is divisible by 2?

		if (number < 2) {
			return false;
		}

		for (int i = 2; i <= number - 1; i++) {
			if (number % i == 0) {
				return false;
			}
		}

		return true;
	}

	public int sumUptoN() {
		int sum = 0;

		for (int i = 1; i <= number; i++) {
			sum = sum + i;
		}

		return sum;
	}

	public int sumOfDivisors() {
		// 6 except 1 , 6 => 2,3
		// 2 + 3 + 4 + 5

		int sum = 0;

		for (int i = 2; i <= number - 1; i++) {
			if (number % i == 0) {
				sum = sum + i;
			}
		}

		return sum;
	}

	public void printNumberTriangle() {
		// 1
		// 1 2
		// 1 2 3
		// 1 2 3 4
		// 1 2 3 4 5

		for (int i = 1; i <= number; i++) {
			for (int j = 1; j <= i; j++) {
				System.out.print(j + " ");
			}
			System.out.println();
		}

	}

}

/08-Loops/src/com/in28minutes/loops/MyNumberRunner.java

package com.in28minutes.loops;

import com.in28minutes.loops.MyNumber;

public class MyNumberRunner {

	public static void main(String[] args) {
		MyNumber number = new MyNumber(5);
		
		boolean isPrime = number.isPrime();
		System.out.println("isPrime " + isPrime);
		
		int sum = number.sumUptoN();
		System.out.println("sumUptoN " + sum);
		
		int sumOfDivisors = number.sumOfDivisors();
		System.out.println("sumOfDivisors " + sumOfDivisors);
		
		number.printNumberTriangle();
	}

}

/08-Loops/src/com/in28minutes/loops/WhileNumberPlayer.java

package com.in28minutes.loops;

public class WhileNumberPlayer {

	private int limit;

	public WhileNumberPlayer(int limit) {
		this.limit = limit;
	}

	// For limit = 30, output would be 1 4 9 16 25
	public void printSquaresUptoLimit() {
		int i = 1;
		while (i * i < limit) {
			System.out.print(i * i + " ");
			i++;
		}
		System.out.println();
	}

	// For limit = 27, output would be 1 8 27
	public void printCubesUptoLimit() {
		int i = 1;
		while (i * i * i <= limit) {
			System.out.print(i * i * i + " ");
			i++;
		}
		System.out.println();
	}

}

/08-Loops/src/com/in28minutes/loops/WhileNumberPlayerRunner.java

package com.in28minutes.loops;

public class WhileNumberPlayerRunner {
	public static void main(String[] args) {
		WhileNumberPlayer player = new WhileNumberPlayer(27);
		player.printSquaresUptoLimit();
		player.printCubesUptoLimit();
	}
}

09-ReferenceTypes

Steps

Step 00 - Java Reference Types - Section Introduction
Step 01 - Reference Types - How are they stored in Memory?
Step 02 - Java Reference Types - Puzzles
Step 03 - String class - Introduction and Exercise - Print each word and char on a new line
Step 04 - String class - Exercise Solution and Some More Important Methods
Step 05 - Understanding String is Immutable and String Concat, Upper Case, Lower Case, Trim methods
Step 06 - String Concatenation and Join, Replace Methods
Step 07 - Java String Alternatives - StringBuffer and StringBuilder
Step 08 - Java Wrapper Classes - An Introduction - Why and What?
Step 09 - Java Wrapper Classes - Creation - Constructor and valueOf
Step 10 - Java Wrapper Classes - Auto Boxing and a Few Wrapper Constants - SIZE, BYTES, MAX_VALUE and MIN_VALUE
Step 11 - Java Dates - Introduction to LocalDate, LocalTime and LocalDateTime
Step 12 - Java Dates - Exploring LocalDate - Creation and Methods to play with Date
Step 13 - Java Dates - Exploring LocalDate - Comparing Dates and Creating Specific Dates
Step 14 - Java Reference Types - Conclusion

Exercises

String

Take a piece of Text into a String.
- Print each character in the text on a seperate line
- Print each word in the text on a seperate line

Code Examples

/09-ReferenceTypes/commands.txt

class Planet {
}
Planet jupiter = new Planet();
int i = 5;
class Animal {
    int id;
    Animal(int id) {
       this.id = id;
    }
}
Animal nothing;
nothing = cat
nothing.id = 10
cat.id
nothing = dog
nothing.id
int j = i;
j = 6
i
i == j
j = 5
i == j
Animal dog = new Animal(12);
Animal cat = new Animal(10);
Animal ref = cat;
Animal dog2 = new Animal(12);
cat == dog
cat == ref
dog == dog2
1
2
12.34
"Test".length()
BigDecimal bd = new BigDecimal("1.0");
str.charAt(0)
str.charAt(2)
str.charAt(3)
String biggerString = "This is a lot of text";
str.substring(5)
biggerString.substring(5)
biggerString.substring(5,13)
str.charAt(13)
biggerString.charAt(13)
biggerString.charAt(456)
someString.length()
someString.charAt(5)
for(int i= 0; i<someString.length(); i++) {
    System.out.println(someString.charAt(i));
}
someString.indexOf("lot")
someString.charAt(10)
someString.charAt('i')
someString.indexOf('i')
someString.lastIndexOf('i')
someString.contains("text")
String someString = "This is a lot of text again";
someString.startsWith("This")
someString.startsWith("jfsdklfj")
someString.endsWith("jfsdklfj")
someString.endsWith("in")
someString.endsWith("ain")
someString.endsWith("again")
someString.endsWith("againfsda")
someString.isEmpty()
"fjsadlkfj".isEmpty()
"".isEmpty()
"true".equals("true")
"value".equals("value")
str.equals("value")
str.equals("VAlue")
str.equalsIgnoreCase("VAlue")
str.concat("is awesome");
str
String anotherString = str.concat(" is awesome");
str
anotherString
String string2 = anotherString.concat(".");
str
anotherString
string2
str.toUpperCase()
str.toLowerCase()
str2.trim()
String str2 = "  in28Minutes is awesome.   ";
str2.trim()
1 + 2
"1" + "2"
"1" + 2
"1" + 23
1 + 23
1 + 2 + "3"
"1" + 2 + 3
System.out.println("Value is " + 20)
System.out.println("Value is " + 20 + 20)
System.out.println("Value is " + (20 + 20))
String.join(",", "2", "3", "4")
String.join(",", "A", "B","C")
String.join(",", "A")
String.join(",", "A", "B")
"abcd".replace('a', 'z');
"abcd".replace("ab", "xyz");
String str = "jdsfja ";
"123" + "123" + "1234" + "123456"
sb.append(" 123")
sb
sb
sb.setCharAt(1,'e')
sb
StringBuilder sb = new StringBuilder("test");
Integer integer1 = new Integer("5234");
Integer integer2 = new Integer("5234");
Integer i1 = new Integer(5);
Integer i2 = new Integer(5);
Integer i3 = Integer.valueOf(5);
Integer i4 = Integer.valueOf(5);
i1 == i2
i3 == i4
Integer integer = Integer.valueOf("4567");
int i = integer.intValue();
Float f = Float.valueOf("12.45");
f.floatValue()
f.intValue()
Integer eight = Integer.valueOf(8);
Integer.toBinaryString(eight);
Integer.toHexString(eight);
Integer eightyEight = Integer.valueOf(88);
Integer.toHexString(eightyEight);
seven++
seven
seven == sevenAgain
Integer seven = 7;
Integer sevenAgain = 7;
seven == sevenAgain
Integer.MAX_VALUE
Integer.MIN_VALUE
Integer.SIZE
Integer.BYTES
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.*;
today.getYear()
today.getDayOfWeek()
today.getDayOfMonth()
today.getDayOfYear()
today.getMonth()
today.getMonthValue()
today.isLeapYear()
today.lengthOfYear()
today.lengthOfMonth()
today.plusDays(100)
today.plusMonths(100)
today.plusYears(100)
today.minusYears(100)
LocalDate hundredYearsBefore = today.minusYears(100);
today
LocalDateTime now = LocalDateTime.now();
LocalDate today = LocalDate.now();
LocalDate yesterady = LocalDate.of(2018, 01, 31);
LocalDate yesterday = LocalDate.of(2018, 01, 31);
today
yesterday
today.withYear(2016)
today.withDayOfMonth(20)
today.withMonth(3)
today.withDayOfYear(120)
today.isBefore(yesterday)
today.isAfter(yesterday)

10-ArraysAndArrayList

Steps

Step 00 - Introduction to Array and ArrayList - Section Introduction with a Challenge
Step 01 - Understanding the need and Basics about an Array
Step 02 - Java Arrays - Creating and Accessing Values - Introduction
Step 03 - Java Arrays - Puzzles - Arrays of Objects, Primitive Data Types, toString and Exceptions
Step 04 - Java Arrays - Compare, Sort and Fill
Step 05 - Java Arrays - Exercise - Create Student Class - Part 1 - Total and Average Marks
Step 06 - Java Arrays - Exercise - Create Student Class - Part 2 - Maximum and Minimum Mark
Step 07 - Introduction to Variable Arguments - Need
Step 08 - Introduction to Variable Arguments - Basics
Step 09 - Introduction to Variable Arguments - Enhancing Student Class
Step 10 - Java Arrays - Using Person Objects and String Elements with Exercises
Step 11 - Java String Arrays - Exercise Solutions - Print Day of Week with Most number of letters and more
Step 12 - Adding and Removing Marks - Problem with Arrays
Step 13 - First Look at ArrayList - An Introduction
Step 14 - First Look at ArrayList - Refactoring Student Class to use ArrayList
Step 15 - First Look at ArrayList - Enhancing Student Class with Add and Remove Marks
Step 16 - Introduction to Array and ArrayList - Conclusion

Exercises

Student Class

Student student = new Student (name, list of marks);
int number = student.getNumberOfMarks();
int sum = student.getTotalSumOfMarks();
int maximumMark = student.getMaximumMark();
int minimumMark = student.getMinimumMark();
BigDecimal average = student.getAverageMarks();
student.addNewMark(35);
student.removeMarkAtIndex(5);

String Arrays

Create a string array with days of the week
- "Sunday", "Monday", "Tuesday", "Wednesday"
- "Thursday", "Friday", "Saturday"
Find the day with most number of letters in it
- Longest String
Print days of the week backwards

Code Examples

/10-ArraysAndArrayList/src/com/in28minutes/arrays/StringRunner.java

package com.in28minutes.arrays;

public class StringRunner {

	public static void main(String[] args) {

		String[] daysOfWeek = { "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday" };

		String dayWithMostCharacters = "";

		for (String day : daysOfWeek) {
			if (day.length() > dayWithMostCharacters.length()) {
				dayWithMostCharacters = day;
			}
		}

		System.out.println("Day with Most number of characters " + dayWithMostCharacters);

		for (int i = daysOfWeek.length - 1; i >= 0; i--) {
			System.out.println(daysOfWeek[i]);
		}

	}

}

/10-ArraysAndArrayList/src/com/in28minutes/arrays/Student.java

package com.in28minutes.arrays;

import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.ArrayList;
import java.util.Collections;

public class Student {

	private String name;
	private ArrayList<Integer> marks = new ArrayList<Integer>();

	public Student(String name, int... marks) {
		this.name = name;

		for (int mark : marks) {
			this.marks.add(mark);
		}
	}

	public int getNumberOfMarks() {
		return marks.size();
	}

	public int getTotalSumOfMarks() {
		int sum = 0;
		for (int mark : marks) {
			sum += mark;
		}
		return sum;
	}

	public int getMaximumMark() {
		return Collections.max(marks);
	}

	public int getMinimumMark() {
		return Collections.min(marks);
	}

	public BigDecimal getAverageMarks() {
		int sum = getTotalSumOfMarks();
		int number = getNumberOfMarks();

		return new BigDecimal(sum).divide(new BigDecimal(number), 3, RoundingMode.UP);
	}

	public String toString() {
		return name + marks;
	}

	public void addNewMark(int mark) {
		marks.add(mark);
	}

	public void removeMarkAtIndex(int index) {
		marks.remove(index);
		
	}
}

/10-ArraysAndArrayList/src/com/in28minutes/arrays/StudentRunner.java

package com.in28minutes.arrays;

import java.math.BigDecimal;

public class StudentRunner {

	public static void main(String[] args) {
				
		Student student = new Student("Ranga", 97, 98, 100);
				
		int number = student.getNumberOfMarks();
		System.out.println("number of marks : " + number);
		
		int sum = student.getTotalSumOfMarks();
		System.out.println("sum of marks : " + sum);
		
		int maximumMark = student.getMaximumMark();
		System.out.println("maximum of marks : " + maximumMark);
		
		int minimumMark = student.getMinimumMark();
		System.out.println("minimum of marks : " + minimumMark);
		
		BigDecimal average = student.getAverageMarks();
		System.out.println("average : " + average);
		
		System.out.println(student);
		
		student.addNewMark(35);
		
		System.out.println(student);

		student.removeMarkAtIndex(1);
		
		System.out.println(student);
		
	}

}

11-ObjectOrientedProgrammingAgain

Steps

Step 00 - Object Oriented Programming - Level 2 - Section Introduction
Step 01 - Basics of Designing a Class - Class, Object, State and Behavior
Step 02 - OOPS Example - Fan Class - Deciding State and Constructors
Step 03 - OOPS Example - Fan Class - Deciding Behavior with Methods
Step 04 - OOPS Exercise - Rectangle Class
Step 05 - Understanding Object Composition with Customer Address Example
Step 06 - Understanding Object Composition - An Exercise - Books and Reviews
Step 07 - Understanding Inheritance - Why do we need it?
Step 08 - Object is at top of Inheritance Hierarchy
Step 09 - Inheritance and Overriding - with toString() method
Step 10 - Java Inheritance - Exercise - Student and Employee Classes
Step 11 - Java Inheritance - Default Constructors and super() method call
Step 12 - Java Inheritance - Puzzles - Multiple Inheritance, Reference Variables and instanceof
Step 13 - Java Abstract Class - Introductio
Step 14 - Java Abstract Class - First Example - Creating Recipes with Template Method
Step 15 - Java Abstract Class - Puzzles
Step 16 - Java Interface - Example 1 - Gaming Console - How to think about Intefaces?
Step 17 - Java Interface - Example 2 - Complex Algorithm - API defined by external team
Step 18 - Java Interface - Puzzles - Unimplemented methods, Abstract Classes, Variables, Default Methods and more
Step 19 - Java Interface vs Abstract Class - A Comparison
Step 20 - Java Interface Flyable and Abstract Class Animal - An Exercise
Step 21 - Polymorphism - An introduction

Exercises

Creating a simple class

public class Rectangle
- length, width;
- What constructors?
- What Operations?

Object Composition - Book and Reviews

Object Composition

Book - id, name, author
- Reviews - id, description, rating

 Book book = 
    new Book(123, "Object Oriented Programming with Java", 
          "Ranga");
 book.addReview(
    new Review(10, "Great Book", 5));
 book.addReview(
    new Review(101, "Awesome", 5);

 System.out.println(book);

Inheritance

Setup an Inheritance Hierarchy and implement toString in Employee class

Person
- name,phone,email;
Student
- college, class
Employee
- title, employer, employeeGrade, salary
- toString (print all values including those of Person)

Interface and Abstract Class

interface Flyable

void fly();
Bird "with wings"
Aeroplane "with fuel"
Flyable flyingObjects = {new Bird(), new Aeroplane()};
Loop and invoke fly method

abstract class Animal

void bark()
Dog "Bow Bow"
Cat "Meow Meow"
Animal[] animals = {new Cat(), new Dog()};
Loop and invoke bark method

Code Examples

/commands.txt

class Pet extends Animal {
     public void groom() {
        System.out.println("Groom");
     }
}
dog.toString()
dog.groom()
Pet pet = new Dog();
pet.groom()
pet instanceof Pet
pet instanceof Dog
pet instanceof Animal
pet instanceof Object
animal instanceof Pet
animal instanceof Dog
animal instanceof Object
class Animal {
   public void bark() {
       System.out.println("TEst");
   }
}
animal.bark()
abstract class AbstractAnimal {
    abstract public void bark();
}
class Dog extends AbstractAnimal {
    public void bark() {
       System.out.println("Bow Bow");
    }
}
Dog dog = new Dog();
dog.bark()
abstract class AbstractTest {
}
abstract class Algorithm1 extends AbstractAlgorithm {
}
abstract class AbstractAlgorithm {
     private int stepCount;
     public int getStepCount() {
          return stepCount();
     }
}
class Implementation implements Interface2 {
   public void method2() { }
   public void method1() { }
}
abstract class ImplementationAbstract implements Interface2 {
   public void method1() { }
}
interface Interface3 {
  int test = 5;
}
interface Interface4 {
    default void print() {
       System.out.println("default");
    }
}
class Test implements Interface4 {
}
test.print()
class Test1 implements Interface4 {
   public void print() {
      System.out.println("override");
   }
}
Test1 test = new Test1();
test.print()
interface Interface1 {
 void method1();
}
interface Interface2 {
 void method2();
}

/src/com/in28minutes/oops/level2/AbstractRecipe.java

package com.in28minutes.oops.level2;

public abstract class AbstractRecipe {
	
	public void execute() {
		getReady();
		doTheDish();
		cleanup();
	}
	
	abstract void getReady();
	abstract void doTheDish();
	abstract void cleanup();
}

/src/com/in28minutes/oops/level2/Address.java

package com.in28minutes.oops.level2;

public class Address {
	private String line1;
	private String city;
	private String zip;
	
	//creation
	public Address(String line1, String city, String zip) {
		super();
		this.line1 = line1;
		this.city = city;
		this.zip = zip;
	}
	
	public String toString() {
		return line1 + " " + city + " " + zip;
				 
	}
	
}

/src/com/in28minutes/oops/level2/Book.java

package com.in28minutes.oops.level2;

import java.util.ArrayList;

public class Book {

	private int id;
	private String name;
	private String author;
	private ArrayList<Review> reviews = new ArrayList<>();

	public Book(int id, String name, String author) {
		this.id = id;
		this.name = name;
		this.author = author;
	}

	public void addReview(Review review) {
		this.reviews.add(review);
	}
	
	public String toString() {
		return String.format("id =%d name = %s author = %s Reviews = [%s]",
				id, name, author, reviews);
	}

}

/src/com/in28minutes/oops/level2/BookRunner.java

package com.in28minutes.oops.level2;

public class BookRunner {

	public static void main(String[] args) {
		Book book = new Book(123, "Object Oriented Programming with Java",
				"Ranga");
		book.addReview(new Review(10, "Great Book", 5));
		book.addReview(new Review(101, "Awesome", 5));

		System.out.println(book);

	}

}

/src/com/in28minutes/oops/level2/Customer.java

package com.in28minutes.oops.level2;

public class Customer {

	//state
	private String name;
	private Address homeAddress;
	private Address workAddress;
	
	//creating
	public Customer(String name, Address homeAddress) {
		this.name = name;
		this.homeAddress = homeAddress;
	}

	//operations
	public Address getHomeAddress() {
		return homeAddress;
	}

	public void setHomeAddress(Address homeAddress) {
		this.homeAddress = homeAddress;
	}

	public Address getWorkAddress() {
		return workAddress;
	}

	public void setWorkAddress(Address workAddress) {
		this.workAddress = workAddress;
	}
		
	public String toString() {
		return String.format("name - [%s] home address - [%s] work address - [%s])"
				, name, homeAddress, workAddress);
	}
	
}

/src/com/in28minutes/oops/level2/CustomerRunner.java

package com.in28minutes.oops.level2;

public class CustomerRunner {

	public static void main(String[] args) {
		Address homeAddress = new Address("line 1", "Hyderabad", "500035");
		Customer customer = new Customer("Ranga", homeAddress);
		System.out.println(customer);
		
		Address workAddress = new Address("line 1 for work", "Hyderabad", "500078");
		customer.setWorkAddress(workAddress);
		
		System.out.println(customer);
	}	
}

/src/com/in28minutes/oops/level2/Fan.java

package com.in28minutes.oops.level2;

public class Fan {
	
	//state
	private String make;
	private double radius;
	private String color;

	private boolean isOn;
	private byte speed; //0 to 5
	
	//creation
	public Fan(String make, double radius, String color) {
		this.make = make;
		this.radius = radius;
		this.color = color;
	}
	
	public void switchOn() {
		this.isOn = true;
		setSpeed((byte)5);
	}

	public void switchOff() {
		this.isOn = false;
		setSpeed((byte)0);
	}

	public void setSpeed(byte speed) {
		this.speed = speed;
	}
	
	//print the state
	public String toString() {
		return String.format("make - %s, radius - %f , color - %s , isOn - %b , speed - %d", 
				make, radius, color, isOn, speed);
	}
	
}

/src/com/in28minutes/oops/level2/FanRunner.java

package com.in28minutes.oops.level2;

public class FanRunner {
	public static void main(String[] args) {
		Fan fan = new Fan("Manufacturer 1", 0.34567, "GREEN");
		fan.switchOn();
		System.out.println(fan);
		fan.setSpeed((byte)3);
		System.out.println(fan);
		fan.switchOff();
		System.out.println(fan);
	}
}

/src/com/in28minutes/oops/level2/inheritance/AnimalRunner.java

package com.in28minutes.oops.level2.inheritance;

abstract class Animal {
	abstract void bark();
}

class Dog extends Animal {
	public void bark() {
		System.out.println("Bow Bow");
	}
}

class Cat extends Animal {
	public void bark() {
		System.out.println("Meow Meow");
	}
}

public class AnimalRunner {
	public static void main(String[] args) {
		Animal[] animals = {new Cat(), new Dog()};
		for(Animal animal:animals) {
			animal.bark();
		}

	}

}

/src/com/in28minutes/oops/level2/inheritance/Employee.java

package com.in28minutes.oops.level2.inheritance;

import java.math.BigDecimal;

public class Employee extends Person {
	private String title;
	private String employerName;
	private char employeeGrade;
	private BigDecimal salary;
	
	public Employee(String name, String title) {
		super(name);
		this.title = title;
		System.out.println("Employee Constructor");
	}

	public String getTitle() {
		return title;
	}

	public void setTitle(String title) {
		this.title = title;
	}

	public String getEmployerName() {
		return employerName;
	}

	public void setEmployerName(String employerName) {
		this.employerName = employerName;
	}

	public char getEmployeeGrade() {
		return employeeGrade;
	}

	public void setEmployeeGrade(char employeeGrade) {
		this.employeeGrade = employeeGrade;
	}

	public BigDecimal getSalary() {
		return salary;
	}

	public void setSalary(BigDecimal salary) {
		this.salary = salary;
	}

	public String toString() {
        return super.toString() + "#" + title + "#" + employerName + "#" + employeeGrade;
    }

}

/src/com/in28minutes/oops/level2/inheritance/Person.java

package com.in28minutes.oops.level2.inheritance;

public class Person extends Object{
	private String name;
	private String email;
	private String phoneNumber;
		
	public Person(String name) {
		System.out.println("Person Constructor");
		this.name = name;
	}
	
	public String getName() {
		return name;
	}

	public String getEmail() {
		return email;
	}

	public void setEmail(String email) {
		this.email = email;
	}

	public String getPhoneNumber() {
		return phoneNumber;
	}

	public void setPhoneNumber(String phoneNumber) {
		this.phoneNumber = phoneNumber;
	}
	
	public String toString() {
        return name + "#" + email + "#" + phoneNumber;
    }
}

/src/com/in28minutes/oops/level2/inheritance/Student.java

package com.in28minutes.oops.level2.inheritance;

public class Student extends Person {
	private String collegeName;
	private int year;

	public Student(String name, String collegeName) {
		super(name);
		this.collegeName = collegeName;
	}
	
	public String getCollegeName() {
		return collegeName;
	}

	public void setCollegeName(String collegeName) {
		this.collegeName = collegeName;
	}

	public int getYear() {
		return year;
	}

	public void setYear(int year) {
		this.year = year;
	}

}

/src/com/in28minutes/oops/level2/inheritance/StudentRunner.java

package com.in28minutes.oops.level2.inheritance;

public class StudentRunner {

	public static void main(String[] args) {
		
		//Student student = new Student();
		//student.setName("Ranga");
		//student.setEmail("in28minutes@gmail.com");
		
		/*
		Person person = new Person();
		person.setName("Ranga");
		person.setEmail("ranga@in28minutes.com");
		person.setPhoneNumber("123-456-7890");
		String value = person.toString();
		System.out.println(value);
		System.out.println(person);
		*/
		
		Employee employee = new Employee("Ranga", "Programmer Analyst");
		//employee.setName("Ranga");
		employee.setEmail("ranga@in28minutes.com");
		employee.setPhoneNumber("123-456-7890");
		employee.setEmployeeGrade('A');
		employee.setTitle("Programmer Analyst");
		
		System.out.print(employee);
		
	}
}

/src/com/in28minutes/oops/level2/inheritance/StudentWithoutInheritance.java

package com.in28minutes.oops.level2.inheritance;

public class StudentWithoutInheritance {
	private String name;
	private String email;
	private String phoneNumber;
	
	private String college;
	private int year;

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getEmail() {
		return email;
	}

	public void setEmail(String email) {
		this.email = email;
	}

	public String getPhoneNumber() {
		return phoneNumber;
	}

	public void setPhoneNumber(String phoneNumber) {
		this.phoneNumber = phoneNumber;
	}

	public String getCollege() {
		return college;
	}

	public void setCollege(String college) {
		this.college = college;
	}

	public int getYear() {
		return year;
	}

	public void setYear(int year) {
		this.year = year;
	}

	
	
}

/src/com/in28minutes/oops/level2/interfaces/ChessGame.java

package com.in28minutes.oops.level2.interfaces;

public class ChessGame implements GamingConsole{

	@Override
	public void up() {
		System.out.println("Move piece up");
	}

	@Override
	public void down() {
		System.out.println("Move piece down");
	}

	@Override
	public void left() {
		System.out.println("Move piece left");
	}

	@Override
	public void right() {
		System.out.println("Move piece right");
	}
	
}

/src/com/in28minutes/oops/level2/interfaces/ComplexAlgorithm.java

package com.in28minutes.oops.level2.interfaces;

public interface ComplexAlgorithm {
	int complexAlgorithm(int number1, int number2);
}

/src/com/in28minutes/oops/level2/interfaces/DummyAlgorithm.java

package com.in28minutes.oops.level2.interfaces;

public class DummyAlgorithm implements ComplexAlgorithm{

	@Override
	public int complexAlgorithm(int number1, int number2) {
		return number1 + number2;
	}

}

/src/com/in28minutes/oops/level2/interfaces/FlyableRunner.java

package com.in28minutes.oops.level2.interfaces;

interface Flyable{
	void fly();
}

class Bird implements Flyable{

	@Override
	public void fly() {
		System.out.println("with wings");
	}
	
}

class Aeroplane implements Flyable{

	@Override
	public void fly() {
		System.out.println("with fuel");
	}
	
}

public class FlyableRunner {

	public static void main(String[] args) {
		Flyable[] flyingObjects = { new Bird(), new Aeroplane()};
		for(Flyable object : flyingObjects) {
			object.fly();
		}
	}

}

/src/com/in28minutes/oops/level2/interfaces/GameRunner.java

package com.in28minutes.oops.level2.interfaces;

public class GameRunner {

	public static void main(String[] args) {
		GamingConsole[] games = {new MarioGame(), new ChessGame()};
		
		for(GamingConsole game:games) {
			game.up();
			game.down();
			game.left();
			game.right();
		}

	}

}

/src/com/in28minutes/oops/level2/interfaces/GamingConsole.java

package com.in28minutes.oops.level2.interfaces;

public interface GamingConsole {
	public void up();
	public void down();
	public void left();
	public void right();
}

/src/com/in28minutes/oops/level2/interfaces/MarioGame.java

package com.in28minutes.oops.level2.interfaces;

public class MarioGame implements GamingConsole{

	@Override
	public void up() {
		System.out.println("Jump");
	}

	@Override
	public void down() {
		System.out.println("Goes into a hole");
	}

	@Override
	public void left() {
	}

	@Override
	public void right() {
		System.out.println("Go Forward");
	}
	
}

/src/com/in28minutes/oops/level2/interfaces/Project.java

package com.in28minutes.oops.level2.interfaces;

public class Project {

	interface Test {
		void nothing();

		default void nothing1() {

		}

	}

	class Class1 implements Test {

		@Override
		public void nothing() {
			// TODO Auto-generated method stub

		}

	}

	class Class2 implements Test {

		@Override
		public void nothing() {
			// TODO Auto-generated method stub

		}

	}

	public static void main(String[] args) {
		ComplexAlgorithm algorithm = new RealAlgorithm();
		System.out.println(algorithm.complexAlgorithm(10, 20));
	}

}

/src/com/in28minutes/oops/level2/interfaces/RealAlgorithm.java

package com.in28minutes.oops.level2.interfaces;

public class RealAlgorithm implements ComplexAlgorithm{

	@Override
	public int complexAlgorithm(int number1, int number2) {
		return number1 * number2;
	}

}

/src/com/in28minutes/oops/level2/Recipe1.java

package com.in28minutes.oops.level2;

public class Recipe1 extends AbstractRecipe{

	@Override
	void getReady() {
		System.out.println("Get the raw materials");
		System.out.println("Get the utensils");
	}

	@Override
	void doTheDish() {
		System.out.println("do the dish");
	}

	@Override
	void cleanup() {
		System.out.println("Cleanup the utensils");		
	}

}

/src/com/in28minutes/oops/level2/RecipeRunner.java

package com.in28minutes.oops.level2;

public class RecipeRunner {

	public static void main(String[] args) {
		Recipe1 recipe = new Recipe1();
		recipe.execute();

		RecipeWithMicrowave recipeWithMicrowave = new RecipeWithMicrowave();
		recipeWithMicrowave.execute();

	}

}

/src/com/in28minutes/oops/level2/RecipeWithMicrowave.java

package com.in28minutes.oops.level2;

public class RecipeWithMicrowave extends AbstractRecipe{

	@Override
	void getReady() {
		System.out.println("Get the raw materials");
		System.out.println("Switch on the microwave");
	}

	@Override
	void doTheDish() {
		System.out.println("get stuff ready");
		System.out.println("Put it in the microwave");
	}

	@Override
	void cleanup() {
		System.out.println("Cleanup the utensils");
		System.out.println("Switch off the microwave");
	}

}

/src/com/in28minutes/oops/level2/Rectangle.java

package com.in28minutes.oops.level2;

public class Rectangle {

	//state
	private int length;
	private int width;
	
	//creation
	public Rectangle(int length, int width) {
		this.length = length;
		this.width = width;
	}


	//operations
	public int getLength() {
		return length;
	}

	public void setLength(int length) {
		this.length = length;
	}

	public int getWidth() {
		return width;
	}

	public void setWidth(int width) {
		this.width = width;
	}
		
	public int area() {
		return length * width;
	}
	
	public int perimeter() {
		return 2 * (length + width);
	}
	
	public String toString() {
		return String.format("length - %d width - %d area - %d perimeter - %d", 
				length, width, area(), perimeter());
	}
}

/src/com/in28minutes/oops/level2/RectangleRunner.java

package com.in28minutes.oops.level2;

public class RectangleRunner {

	public static void main(String[] args) {
		Rectangle rectangle = new Rectangle(12, 23);
		System.out.println(rectangle);
		rectangle.setWidth(25);
		System.out.println(rectangle);
	}

}

/src/com/in28minutes/oops/level2/Review.java

package com.in28minutes.oops.level2;

public class Review {

	private int id;
	private String description;
	private int rating;

	public Review(int id, String description, int rating) {
		this.id = id;
		this.description = description;
		this.rating = rating;
	}
	
	public String toString() {
		return id + " " + description + " " + rating;
	}

}

12-Collections

Steps

Step 01 - Java Collections - Section Overview with Need For Collections
Step 02 - List Interface - Introduction - Position is King
Step 03 - List Inteface - Immutability and Introduction of Implementations - ArrayList, LinkedList and Vector
Step 04 - List Inteface Implementations - ArrayList vs LinkedList
Step 05 - List Inteface Implementations - ArrayList vs Vector
Step 06 - List Inteface - Methods to add, remove and change elements and lists
Step 07 - List and ArrayList - Iterating around elements
Step 08 - List and ArrayList - Choosing iteration approach for printing and deleting elements
Step 09 - List and ArrayList - Puzzles - Type Safety and Removing Integers
Step 10 - List and ArrayList - Sorting - Introduction to Collections sort static method
Step 11 - List and ArrayList - Sorting - Implementing Comparable Inteface in Student Class
Step 12 - List and ArrayList - Sorting - Providing Flexibility by implementing Comparator interface
Step 13 - List and ArrayList - A Summary
Step 14 - Set Interface - Introduction - No Duplication
Step 15 - Understanding Data Structures - Array, LinkedList and Hashing
Step 16 - Understanding Data Structures - Tree - Sorted Order
Step 17 - Set Interface - Hands on - HashSet, LinkedHashSet and TreeSet
Step 18 - Set Interface - Exercise - Find Unique Characters in a List
Step 19 - TreeSet - Methods from NavigableSet - floor,lower,upper, subSet, head and tailSet
Step 20 - Queue Interface - Process Elements in Order
Step 21 - Introduction to PriorityQueue - Basic Methods and Customized Priority
Step 22 - Map Interface - An Introduction - Key and Value
Step 23 - Map Interface - Implementations - HashMap, HashTable, LinkedHashMap and TreeMap
Step 24 - Map Interface - Basic Operations
Step 25 - Map Interface - Comparison - HashMap vs LinkedHashMap vs TreeMap
Step 26 - Map Interface - Exercise - Count occurances of characters and words in a piece of text
Step 27 - TreeMap - Methods from NavigableMap - floorKey, higherKey, firstEntry, subMap and more
Step 28 - Java Collections - Conclusion with Three Tips

Exercises

Set Interface

Find unique characters in a list of characters
- In Insertion Order
- In Sort Order

Map Interface

Find number of occurances of each character and word in a piece of text.

Code Examples

/12-Collections/commands.txt

words.size()
words.isEmpty()
words.get(0)
words.contains("Dog");
words.contains("Cat");
words.indexOf("Cat")
words
words.indexOf("Dog")
words.add("Dog")
List<String> wordsLinkedList = new LinkedList<String>(words);
List<String> wordsVector = new Vector<String>(words);
wordsArrayList.add("Dog")
wordsArrayList
wordsArrayList.add("Elephant")
wordsArrayList.add(2, "Ball")
wordsArrayList
wordsArrayList.add("Ball")
wordsArrayList
List<String> newList = List.of("Yak","Zebra");
wordsArrayList.addAll(newList)
wordsArrayList
wordsArrayList.set(6, "Fish")
wordsArrayList
wordsArrayList.remove(2)
wordsArrayList
wordsArrayList.remove("Dog")
wordsArrayList
wordsArrayList.remove("Dog")
for(int i=0; i < words.size(); i++) {
     System.out.println(words.get(i));
}
for(String word:words) {
     System.out.println(word);
}
Iterator wordsIterator = words.iterator();
while(wordsIterator.hasNext()) {
      System.out.println(wordsIterator.next());
}
List<String> wordsArrayList = new ArrayList<String>(words);
for(String word:words) {
   if(word.endsWith("at")) {
        words.remove(word);
   }
}
for(String word:wordsArrayList) {
   if(word.endsWith("at")) {
        wordsArrayList.remove(word);
   }
}
wordsArrayList
for(String word:words) {
   if(word.endsWith("at"))
      System.out.println(word);
}
for(String word:wordsAl) {
   if(word.endsWith("at")) {
        words.remove(word);
   }
}
for(String word:wordsAl) {
   if(word.endsWith("at")) {
        wordsAl.remove(word);
   }
}
wordsAl
List<String> words = List.of("Apple", "Bat" , "Cat");
List<String> wordsAl = new ArrayList<>(words);
Iterator<String> iterator = wordsAl.iterator();
while(iterator.hasNext()) {
     if(iterator.next().endsWith("at")) {
          iterator.remove();
     }
}
wordsAl
List value = List.of("A", 'A' , 1, 1.0);
value.get(2)
value.get(2) instanceof Integer
value.get(1) instanceof Character
value.get(3) instanceof Double
numbers.indexOf(101);
numbersAl.indexOf(101)
numbersAl.remove(101);
numbersAl.remove(101)
numbersAl.remove(Integer.valueOf(101))
numbersAl
List<Integer> numbersAl = new ArrayList<>(numbers);
Collections.sort(numbersAl);
numbersAl
set.add("Apple");
Set<String> hashset = new HashSet<>(set);
hashset.add("Apple")
hashset
Set<String> set = Set.of("A", "Z","D", "C", "B");
hashSet.add("A")
hashSet.add("B")
hashSet
hashSet.add("C")
hashSet
hashSet.add("CA")
hashSet
hashSet.add("CAfsadfa")
hashSet
treeSet.add("Cat")
treeSet.add("Bat")
treeSet.add("Apple")
treeSet
hashSet.add("Cat");
hashSet.add("Bat");
hashSet.add("Apple");
hashSet
hashSet.add("Dog");
hashSet
hashSet.add("Elephant");
hashSet.add(5);
hashSet.add(4);
hashSet.add(3);
hashSet.add(2);
hashSet.add(1);
hashSet
Set<Integer> hashSet = new HashSet<>();
hashSet.add(589789);
hashSet.add(58978);
hashSet.add(5897);
hashSet.add(589);
hashSet.add(58);
hashSet.add(5);
hashSet
Set<Integer> linkedHashSet = new LinkedHashSet<>();
linkedHashSet.add(589789);
linkedHashSet.add(58978);
linkedHashSet.add(5897);
linkedHashSet.add(589);
linkedHashSet.add(58);
linkedHashSet.add(5);
linkedHashSet
Set<Integer> treeSet = new TreeSet<>();
treeSet.add(584567);
treeSet.add(58456);
treeSet.add(5845);
treeSet.add(584);
treeSet.add(58);
treeSet.add(5);
treeSet
numbers.add(765432);
numbers.add(76543);
numbers.add(7654);
numbers.add(765);
numbers.add(76);
numbers
numbers.add(765432);
numbers.add(76543);
numbers.add(7654);
numbers.add(765);
numbers.add(76);
numbers
numbers.add(765789);
numbers
numbers.add(76)
numbers
numbers.add(765432);
numbers.add(76543);
numbers.add(7654);
numbers.add(765);
numbers.add(76);
numbers
numbers.add(76)
List<Character> characters = List.of('A','Z','A', 'B', 'Z','F');
TreeSet<Integer> numbers = new TreeSet<>(Set.of(65,54,34,12,99));
numbers.floor(40)
numbers.floor(34)
numbers.lower(34)
numbers.ceiling(34)
numbers.ceiling(36)
numbers.higher(34)
numbers
numbers.subSet(20,80)
numbers.subSet(34,54)
numbers.subSet(34,65)
numbers.subSet(34,true,65,true)
numbers.subSet(34,false,65,false)
numbers.headSet(50)
numbers.tailSet(50)
Queue<String> queue = new PriorityQueue<>();
queue.poll()
queue.offer("Apple")
queue.addAll(List.of("Zebra", "Monkey", "Cat"))
queue
queue.poll()
queue
queue.poll()
queue.poll()
queue.poll()
queue.poll()
map.put("R",1);
map
map.get("Z")
map.get("A")
map.get("C")
map.size()
map.isEmpty()
map.containsKey("A")
map.containsKey("F")
map.containsValue(3)
map
map.containsValue(4)
map.keySet()
map.values()
map
hashmap.put("F",5)
hashmap
hashmap.put("Z",11)
hashmap
Map<String, Integer> map = Map.of("A",3,"Z",5,"B",10);
Map<String, Integer> linkedHashmap = new LinkedHashMap<>(map);
HashMap<String, Integer> hashmap = new HashMap<>();
hashmap.put("Z",5)
hashmap.put("A",15)
hashmap.put("F",25)
hashmap.put("L",250)
hashmap
LinkedHashMap<String, Integer> linkedHashMap = new LinkedHashMap<>();
hashmap
linkedHashMap.put("F",25)
linkedHashMap.put("A",15)
linkedHashMap.put("Z",5)
linkedHashMap.put("L",250)
linkedHashMap
treemap.put("F",25)
treemap.put("A",15)
treemap.put("Z",5)
treemap.put("L",250)
treemap
TreeMap<String, Integer> treemap = new TreeMap<>();
treemap.put("F",25)
treemap.put("Z",5)
treemap.put("L",250)
treemap.put("A",15)
treemap.put("B",25)
treemap.put("G",25)
treemap
treemap.higherKey("C")
treemap.lowerKey("C")
treemap.lowerKey("B")
treemap.floorKey("B")
treemap.higherKey("B")
treemap.higherKey("C")
treemap.ceilingKey("B")
treemap.lowerKey("B")
treemap.floorKey("B")
treemap.firstEntry()
treemap.lastEntry()
treemap
treemap.subMap("C", "Y")
treemap.subMap("B", "Z")
treemap.subMap("B",true, "Z",true)

/12-Collections/src/collections/MapRunner.java

package collections;

import java.util.HashMap;
import java.util.Map;


public class MapRunner {

	public static void main(String[] args) {
		String str = "This is an awesome occasion. "
				+ "This has never happened before.";
		
		Map<Character, Integer> occurances = new HashMap<>();
		
		char[] characters = str.toCharArray();
		
		for(char character:characters) {
			//Get the character
			Integer integer = occurances.get(character);
			if(integer==null) {
				occurances.put(character, 1);
			} else {
				occurances.put(character, integer + 1);
			}
		}
		
		System.out.println(occurances);
		
		Map<String, Integer> stringOccurances = new HashMap<>();
		String[] words = str.split(" ");
		
		
		for(String word:words) {
			//Get the character
			Integer integer = stringOccurances.get(word);
			if(integer==null) {
				stringOccurances.put(word, 1);
			} else {
				stringOccurances.put(word, integer + 1);
			}
		}
		
		System.out.println(stringOccurances);
		
		
	}

}

/12-Collections/src/collections/QueueRunner.java

package collections;

import java.util.Comparator;
import java.util.List;
import java.util.PriorityQueue;
import java.util.Queue;

class StringLengthComparator implements Comparator<String> {
	@Override
	public int compare(String value1, String value2) {
		return Integer.compare(value2.length(),
				value1.length());
	}

}

public class QueueRunner {

	public static void main(String[] args) {
		Queue<String> queue = new PriorityQueue<>(10,
				new StringLengthComparator());
		queue.addAll(List.of("Zebra", "Monkey", "Cat", "A",
				"B", "C", "D", "E", "F", "G"));
		queue.offer("Z");
		while (queue.peek() != null)
			System.out.println(queue.poll());
	}

}

/12-Collections/src/collections/SetRunner.java

package collections;

import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;

public class SetRunner {

	public static void main(String[] args) {
		List<Character> characters = List.of('A','Z','A', 'B', 'Z','F');
		//unique - Set
		// Tree
		// Hash
		// LinkedHash
		
		Set<Character> treeSet = new TreeSet<>(characters);
		System.out.println("treeSet "+ treeSet);

		Set<Character> linkedHashSet = new LinkedHashSet<>(characters);
		System.out.println("linkedHashSet "+ linkedHashSet);
		
		Set<Character> hashSet = new HashSet<>(characters);
		System.out.println("hashSet "+ hashSet);

		

	}

}

/12-Collections/src/collections/Student.java

package collections;

public class Student implements Comparable<Student>{
	private int id;
	private String name;

	public Student(int id, String name) {
		super();
		this.id = id;
		this.name = name;
	}

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String toString() {
		return id + " " + name;
	}

	@Override
	public int compareTo(Student that) {
		return Integer.compare(that.id, this.id);
	}
}

/12-Collections/src/collections/StudentsCollectionRunner.java

package collections;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

class AscendingStudentComparator implements Comparator<Student> {
	@Override
	public int compare(Student student1, Student student2) {
		return Integer.compare(student1.getId(), student2.getId());
	}
}

public class StudentsCollectionRunner {

	public static void main(String[] args) {
		List<Student> students = List.of(new Student(1, "Ranga"),
				new Student(100, "Adam"),
				new Student(2,"Eve"));
		
		ArrayList<Student> studentsAl = new ArrayList<>(students);
		
		System.out.println(studentsAl);
		
		Collections.sort(studentsAl);
		System.out.println("Desc " + studentsAl);
		
		//Collections.sort(studentsAl, new AscendingStudentComparator());
		
		studentsAl.sort(new AscendingStudentComparator());
		System.out.println("AscendingStudentComparator " + studentsAl);	
	}

}

13-Generics

Steps

Step 01 - Introduction to Generics - Why do we need Generics?
Step 02 - Implementing Generics for the Custom List
Step 03 - Extending Custom List with a Generic Return Method
Step 04 - Generics Puzzles - Restrictions with extends and Generic Methods
Step 05 - Generics and WildCards - Upper Bound and Lower Bound

Code Examples

/13-Generics/src/com/in28minutes/generics/GenericsRunner.java

package com.in28minutes.generics;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;

public class GenericsRunner {

	static <X> X doubleValue(X value) {
		return value;
	}

	static <X extends List> void duplicate(X list) {
		list.addAll(list);
	}

	static double sumOfNumberList(
			List<? extends Number> numbers) {
		double sum = 0.0;
		for (Number number : numbers) {
			sum += number.doubleValue();
		}
		return sum;
	}

	static void addACoupleOfValues(
			List<? super Number> numbers) {
		numbers.add(1);
		numbers.add(1.0);
		numbers.add(1.0f);
		numbers.add(1l);
	}

	public static void main(String[] args) {
		List emptyList = new ArrayList<Number>();
		addACoupleOfValues(emptyList);
		System.out.println(emptyList);

		System.out.println(
				sumOfNumberList(List.of(1, 2, 3, 4, 5)));
		System.out.println(sumOfNumberList(
				List.of(1.1, 2.1, 3.1, 4.1, 5.1)));
		System.out.println(sumOfNumberList(
				List.of(1l, 2l, 3l, 4l, 5l)));

		String value1 = doubleValue(new String());
		Integer number1 = doubleValue(Integer.valueOf(5));
		ArrayList list1 = doubleValue(new ArrayList());

		LinkedList<Integer> numbers = new LinkedList<>(
				List.of(1, 2, 3));
		duplicate(numbers);
		System.out.println(numbers);

		MyCustomList<String> list = new MyCustomList<>();
		list.addElement("Element 1");
		list.addElement("Element 2");
		String value = list.get(0);

		System.out.println(value);

		MyCustomList<Integer> list2 = new MyCustomList<>();
		list2.addElement(Integer.valueOf(5));
		list2.addElement(Integer.valueOf(7));
		Integer number = list2.get(0);
		System.out.println(number);

	}

}

/13-Generics/src/com/in28minutes/generics/MyCustomList.java

package com.in28minutes.generics;

import java.util.ArrayList;

public class MyCustomList<T>{
	
	ArrayList<T> list = new ArrayList<>();
	
	public void addElement(T element) {
		list.add(element);
	}
	
	public void removeElement(T element) {
		list.remove(element);
	}
	
	public String toString() {
		return list.toString();
	}

	public T get(int index) {
		return list.get(index);
	}
}

14-FunctionalProgramming

Steps

Step 01 - Introduction to Functional Programming - Functions are First Class Citizens
Step 02 - Functional Programming - First Example with Function as Parameter
Step 03 - Functional Programming - Exercise - Loop a List of Numbers
Step 04 - Functional Programming - Filtering - Exercises to print odd and even numbers from List
Step 05 - Functional Programming - Collect - Sum of Numbers in a List
Step 06 - Functional Programming vs Structural Programming - A Quick Comparison
Step 07 - Functional Programming Terminology - Lambda Expression, Stream and Operations on a Stream
Step 08 - Stream Intermediate Operations - Sort, Distinct, Filter and Map
Step 09 - Stream Intermediate Operations - Exercises - Squares of First 10, Map String List to LowerCase and Length of String
Step 10 - Stream Terminal Operations - 1 - max operation with Comparator
Step 11 - Stream Terminal Operations - 2 - min, collect to List,
Step 12 - Optional class in Java - An Introduction
Step 13 - Behind the Screens with Functional Interfaces - Implement Predicate Interface
Step 14 - Behind the Screens with Functional Interfaces - Implement Consumer Interface
Step 15 - Behind the Screens with Functional Interfaces - Implement Function Inteface for Mapping
Step 16 - Simplify Functional Programming code with Method References - static and instance methods
Step 17 - Functions are First Class Citizens
Step 18 - Introduction to Functional Programming - Conclusion

Exercises

Create a list of numbers
- Print each element using forEach
- Filter Odd and Even numbers
Print squares of first 10 Numbers using IntStream.range(1,11)
List.of("Apple","Ant","Bat").stream()
- Map each to lowercase and print
- Print length (no of characters) of each word using map

Code Examples

/14-FunctionalProgramming/commands.txt

List<Integer> list = List.of(1,4,7,9);
list.stream().forEach(
      element -> System.out.println(element)
)
list.stream().filter(
               element -> element%2 == 1)
list.stream().filter(
               element -> element%2 == 1).
             forEach(
               element -> System.out.println(element))
list.stream().filter(element -> element%2==1).forEach(element->System.out.println(element))
list.stream().filter(element -> element%2==0).forEach(element->System.out.println(element))
numbers.stream().sorted().forEach(e->System.out.println(e));
List<Integer> numbers = List.of(3,5,3,213,45,5,7);
numbers.stream().distinct().forEach(e->System.out.println(e));
numbers.stream().distinct().sorted().forEach(e->System.out.println(e));
numbers.stream().distinct().map(e -> e * e).forEach(e->System.out.println(e));
IntStream.range(1,10).forEach(p->System.out.println(p))
IntStream.range(1,11).forEach(p->System.out.println(p))
IntStream.range(1,11).map(e -> e * e).forEach(p->System.out.println(p))
List.of("Apple", "Ant", "Bat").stream().map(s->s.toLowerCase()).forEach(p -> System.out.println(p))
List.of("Apple", "Ant", "Bat").stream().map(s->s.length()).forEach(p -> System.out.println(p))
IntStream.range(1,11).reduce( 0 , (n1,n2) -> n1+n2)
List.of(23,12,34,53).stream().max((n1,n2) -> Integer.compare(n1,n2))
$24.isPresent()
List.of(23,12,34,53).stream().max((n1,n2) -> Integer.compare(n1,n2)).get()
List.of(23,12,34,53).stream().max((n1,n2) -> Integer.compare(n1,n2)).get()
List.of(23,12,34,53).stream().max((n1,n2) -> Integer.compare(n1,n2)).get()
List.of(23,12,34,53).stream().min((n1,n2) -> Integer.compare(n1,n2)).get()
List.of(23,12,34,53).stream().filter(e -> e%2==1).forEach(e -> System.out.println(e))
List.of(23,12,34,53).stream().filter(e -> e%2==1).collect(Collectors.toList())
List.of(23,12,34,53).stream().filter(e -> e%2==0).collect(Collectors.toList())
IntStream.range(1,11).map(e -> e * e)
List.of(23,12,34,53).stream().filter(e -> e%2==0).collect(Collectors.toList())
IntStream.range(1,10).map(e -> e * e)
IntStream.range(1,10).map(e -> e * e).boxed().collect(Collectors.toList())
IntStream.range(1,11).map(e -> e * e).boxed().collect(Collectors.toList())
List.of(23,45,67,12).stream().filter(n -> n%2==0).max( (n1,n2) -> Integer.compare(n1,n2) )
$39.get()
$39.isPresent()
List.of(23,45,67).stream().filter(n -> n%2==0).max( (n1,n2) -> Integer.compare(n1,n2) )
$42.isPresent()
$42.orElse(0)
$42.orElse(0)
List.of(23,45,67).stream().filter(n -> n%2==0).max( (n1,n2) -> Integer.compare(n1,n2) ).orElse(0)
List.of(23,45,67,34).stream().filter(n -> n%2==0).max( (n1,n2) -> Integer.compare(n1,n2) ).orElse(0)

/14-FunctionalProgramming/src/com/in28minutes/functionalprogramming/FPNumberRunner.java

package com.in28minutes.functionalprogramming;

import java.util.List;

public class FPNumberRunner {

	public static void main(String[] args) {
		List<Integer> numbers = List.of(4,6,8,13,3,15);
		
		//Exercise - Print squares of first 10 numbers!
		//Clue - IntStream.range(1,10)
		
		//List.of("Apple", "Ant", "Bat").stream()
		//Map all of these to lowercase and print them

		//List.of("Apple", "Ant", "Bat").stream()
		//Print the length of each element

		/*
		numbers.stream()
				.forEach( element ->System.out.println(element));*/
		
		int sum = fpSum(numbers);
			
		System.out.println(sum);

	}

	private static int fpSum(List<Integer> numbers) {
		return numbers.stream()
				.reduce(0, 
					(number1, number2) ->  number1 + number2);
	}

	private static int normalSum(List<Integer> numbers) {
		int sum = 0;
		for(int number:numbers) {
			sum += number; 
		}
		return sum;
	}

}

/14-FunctionalProgramming/src/com/in28minutes/functionalprogramming/FunctionalProgrammingRunner.java

package com.in28minutes.functionalprogramming;

import java.util.List;

public class FunctionalProgrammingRunner {

	public static void main(String[] args) {
		List<String> list = List.of("Apple", "Bat", "Cat",
				"Dog");
		printWithFPWithFiltering(list);

	}

	private static void printBasic(List<String> list) {
		for (String string : list) {
			System.out.println(string);
		}
	}

	private static void printBasicWithFiltering(
			List<String> list) {
		for (String string : list) {
			if (string.endsWith("at")) {
				System.out.println(string);
			}
		}
	}

	private static void printWithFP(List<String> list) {
		list.stream().forEach(element -> System.out
				.println("element - " + element));
	}
	
	private static void printWithFPWithFiltering(List<String> list) {
		list.stream()
				.filter(element -> element.endsWith("at"))
			.forEach(element -> System.out.println("element - " + element));
	}

}

/14-FunctionalProgramming/src/com/in28minutes/functionalprogramming/LambdaBehindTheScreensRunner.java

package com.in28minutes.functionalprogramming;

import java.util.List;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;

class EvenNumberPredicate implements Predicate<Integer> {

	@Override
	public boolean test(Integer number) {
		return number%2 == 0;
	}
	
}

class SystemOutConsumer implements Consumer<Integer> {

	@Override
	public void accept(Integer number) {
		System.out.println(number);
	}
	
}

class NumberSquareMapper implements Function<Integer, Integer> {

	@Override
	public Integer apply(Integer number) {
		return number * number;
	}
	
}

public class LambdaBehindTheScreensRunner {
	
	

	public static void main(String[] args) {

		List.of(23,43,34,45,36,48).stream()
		.filter(n -> n%2 ==0)
		.map(n -> n * n)
		.forEach(e -> System.out.println(e));

		List.of(23,43,34,45,36,48).stream()
		.filter(new EvenNumberPredicate())
		.map(new NumberSquareMapper())
		.forEach(new SystemOutConsumer());

		//.map(n -> n * n)
		//<R> Stream<R> map(Function<? super T, ? extends R> mapper);
		// R apply(T t);
		
		//.filter(new EvenNumberPredicate())
		//Stream<T> filter(Predicate<? super T> predicate);
		//boolean test(T t);
		
		//.forEach(e -> System.out.println(e));
		//Consumer<? super T> action
		//void accept(T t);
		
		//1.Storing functions in variables
		//2.Passing functions to methods <=
		//3.Returning functions from methods
		
		Predicate<? super Integer> evenPredicate = createEvenPredicate();
		Predicate<? super Integer> oddPredicate = n -> n%2 ==1;
		
		List.of(23,43,34,45,36,48).stream()
				.filter(evenPredicate)
				.map(n -> n * n)
				.forEach(e -> System.out.println(e));
	}

	private static Predicate<? super Integer> createEvenPredicate() {
		return n -> n%2 ==0;
	}

}

/14-FunctionalProgramming/src/com/in28minutes/functionalprogramming/MethodReferencesRunner.java

package com.in28minutes.functionalprogramming;

import java.util.List;

public class MethodReferencesRunner {

	public static void print(Integer number) {
		System.out.println(number);
	}

	public static void main(String[] args) {
		List.of("Ant", "Bat", "Cat", "Dog", "Elephant")
				.stream().map(s -> s.length())
				.forEach(s -> MethodReferencesRunner
						.print(s));

		List.of("Ant", "Bat", "Cat", "Dog", "Elephant")
				.stream().map(String::length)
				.forEach(MethodReferencesRunner::print);

		List.of(23,45,67,34).stream()
				.filter(n -> n%2==0)
				.max( (n1,n2) -> Integer.compare(n1,n2) )
				.orElse(0);
		
		Integer max = List.of(23, 45, 67, 34).stream()
				.filter(MethodReferencesRunner::isEven)
				.max(Integer::compare)
				.orElse(0);
		
		System.out.println(max);
	}

	public static boolean isEven(Integer number) {
		return number % 2 == 0;
	}

}

/15-

ThreadsAndConcurrency

Steps

Step 01 - Introduction to Threads and MultiThreading - Need for Threads
Step 02 - Creating a Thread for Task1 - Extending Thread Class
Step 03 - Creating a Thread for Task2 - Implement Runnable Interface
Step 04 - Theory - States of a Thread
Step 05 - Placing Priority Requests for Threads
Step 06 - Communication between Threads - join method
Step 07 - Thread utility methods and synchronized keyword - sleep, yield
Step 08 - Need for Controlling the Execution of Threads
Step 09 - Introduction to Executor Service
Step 10 - Executor Service - Customizing number of Threads
Step 11 - Executor Service - Returning a Future from Thread using Callable
Step 12 - Executor Service - Waiting for completion of multiple tasks using invokeAll
Step 13 - Executor Service - Wait for only the fastest task using invokeAny
Step 14 - Threads and MultiThreading - Conclusion

Code Examples

/15-

ThreadsAndConcurrency/src/CallableRunner.java

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

class CallableTask implements Callable<String> {
   
   private String name;

   public CallableTask(String name) {
      this.name = name;
   }
   
   @Override
   public String call() throws Exception {
      Thread.sleep(1000);
      return "Hello " + name;
   }
   
}

public class CallableRunner {

   public static void main(String[] args) throws InterruptedException, ExecutionException {
      ExecutorService executorService = Executors.newFixedThreadPool(1);
      
      Future<String> welcomeFuture = 
            executorService.submit(new CallableTask("in28Minutes"));
      
      System.out.print("\n new CallableTask(\"in28Minutes\") executed");
      
      String welcomeMessage = welcomeFuture.get();
      
      System.out.println(welcomeMessage);
      
      System.out.print("\n Main completed");

   }

}

/15-

ThreadsAndConcurrency/src/ExecutorServiceRunner.java

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

class Task extends Thread {
	
	private int number;

	public Task(int number) {
		this.number = number;
	}
	
	public void run() { //SIGNATURE
		System.out.print("\nTask " + number + " Started");
		
		for(int i=number*100;i<=number*100 + 99; i++) 
			System.out.print(i + " ");
		
		System.out.print("\nTask" + number +  "Done");
	}
}


public class ExecutorServiceRunner {

	public static void main(String[] args) {
		//ExecutorService executorService = Executors.newSingleThreadExecutor();
		ExecutorService executorService = Executors.newFixedThreadPool(5);
		
		executorService.execute(new Task(1));
		executorService.execute(new Task(2));
		executorService.execute(new Task(3));
		executorService.execute(new Task(4));
		executorService.execute(new Task(5));
		executorService.execute(new Task(6));
		executorService.execute(new Task(7));
				
		executorService.shutdown();

	}

}

/15-

ThreadsAndConcurrency/src/MultipleAnyCallableRunner.java

import java.util.List;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

public class MultipleAnyCallableRunner {

	public static void main(String[] args) throws InterruptedException, ExecutionException {
		ExecutorService executorService = Executors.newFixedThreadPool(3);
		
		List<CallableTask> tasks = List.of(
				new CallableTask("in28Minutes"),
				new CallableTask("Ranga"),
				new CallableTask("Adam"));
		
		String result = executorService.invokeAny(tasks);
		
		System.out.println(result);

		executorService.shutdown();
	}

}

/15-

ThreadsAndConcurrency/src/MultipleCallableRunner.java

import java.util.List;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

public class MultipleCallableRunner {

	public static void main(String[] args) throws InterruptedException, ExecutionException {
		ExecutorService executorService = Executors.newFixedThreadPool(3);
		
		List<CallableTask> tasks = List.of(new CallableTask("in28Minutes"), 
				new CallableTask("Ranga"),  new CallableTask("Adam"));
		
		List<Future<String>> results = executorService.invokeAll(tasks);
		
		for(Future<String> result:results) {
			System.out.println(result.get());
		}

		executorService.shutdown();
	}

}

/15-

ThreadsAndConcurrency/src/ThreadBasicsRunner.java

//extends Thread
//implements Runnable

class Task1 extends Thread {
	
	public void run() { //SIGNATURE
		System.out.print("\nTask1 Started");
		
		for(int i=101;i<=199; i++) 
			System.out.print(i + " ");
		
		System.out.print("\nTask1 Done");
	}
}

class Task2 implements Runnable {

	@Override
	public void run() {
		System.out.print("\nTask2 Started");
		
		for(int i=201;i<=299; i++) 
			System.out.print(i + " ");
		
		System.out.print("\nTask2 Done");
		
		
	}
	
}


public class ThreadBasicsRunner {

	public static void main(String[] args) throws InterruptedException {

		//• NEW;
		//• RUNNABLE;
		//• RUNNING;
		//• BLOCKED/WAITING;
		//• TERMINATED/DEAD;
		
		//Task1 - 101 to 199
		System.out.print("\nTask1 Kicked Off");
		Task1 task1 = new Task1();
		task1.setPriority(1);
		task1.start(); //task1.run();
		
		System.out.print("\nTask2 Kicked Off");
		
		Task2 task2 = new Task2();
		Thread task2Thread = new Thread(task2);
		task2Thread.setPriority(10);
		task2Thread.start();	
	
		task1.join();
		task2Thread.join();
		
		System.out.print("\nTask3 Kicked Off");
		
		//Task3
		for(int i=301;i<=399; i++) 
			System.out.print(i + " ");
		
		System.out.print("\nTask3 Done");
		
		System.out.print("\nMain Done");
	}
}

16-ExceptionHandling

Steps

Step 01 - Introduction to Exception Handling - Your Thought Process during Exception Handling
Step 02 - Basics of Exceptions - NullPointerException and StackTrace
Step 03 - Basics of Handling Exceptions - try and catch
Step 04 - Basics of Handling Exceptions - Exception Hierarchy, Matching and Catching Multiple Exceptions
Step 05 - Basics of Handling Exceptions - Need for finally
Step 06 - Basics of Handling Exceptions - Puzzles
Step 07 - Checked Exceptions vs Unchecked Exceptions - An Example
Step 08 - Hierarchy of Errors and Exceptions - Checked and Runtime
Step 09 - Throwing an Exception - Currencies Do Not Match Runtime Exception
Step 10 - Throwing a Checked Exception - Throws in method signature and handling
Step 11 - Throwing a Custom Exception - CurrenciesDoNotMatchException
Step 12 - Write less code with Try with Resources - New Feature in Java 7
Step 13 - Basics of Handling Exceptions - Puzzles 2
Step 14 - Exception Handling - Conclusion with Best Practices

Code Examples

/16-ExceptionHandling/src/com/in28minutes/exceptionhandling/CheckedExceptionRunner.java

package com.in28minutes.exceptionhandling;

public class CheckedExceptionRunner {
	
	public static void main(String[] args) {
	/*	try {
			someOtherMethod();
			Thread.sleep(2000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}*/
		//someOtherMethod1();
		someOtherMethod2();

	}
	
	private static void someOtherMethod2() throws RuntimeException{
		
	}
	
	private static void someOtherMethod() throws InterruptedException{
		Thread.sleep(2000);
	}

}

/16-ExceptionHandling/src/com/in28minutes/exceptionhandling/ExceptionHandlingRunner.java

package com.in28minutes.exceptionhandling;

public class ExceptionHandlingRunner {

	public static void main(String[] args) {
		method1();
		System.out.println("Main Ended");
	}

	private static void method1() {
		method2();
		System.out.println("Method1 Ended");
	}

	private static void method2() {
		String str = null;
		str.length();
		System.out.println("Method2 Ended");
	}
}

/16-ExceptionHandling/src/com/in28minutes/exceptionhandling/ExceptionHandlingRunner2.java

package com.in28minutes.exceptionhandling;

public class ExceptionHandlingRunner2 {

	public static void main(String[] args) {
		method1();
		System.out.println("Main Ended");
	}

	private static void method1() {
		method2();
		System.out.println("Method1 Ended");
	}

	private static void method2() {
		try {
			//String str = null;
			//str.length();
			int[] i = {1,2};
			int number = i[3];
			System.out.println("Method2 Ended");
		} catch (NullPointerException ex) {
			System.out.println("Matched NullPointerException");
			ex.printStackTrace();
		} catch (ArrayIndexOutOfBoundsException ex) {
			System.out.println("Matched ArrayIndexOutOfBoundsException");
			ex.printStackTrace();
		} catch (Exception ex) {
			System.out.println("Matched Exception");
			ex.printStackTrace();
		}
	}
}

/16-ExceptionHandling/src/com/in28minutes/exceptionhandling/FinallyRunner.java

package com.in28minutes.exceptionhandling;

import java.util.Scanner;

public class FinallyRunner {

	public static void main(String[] args) {
		
		Scanner scanner = null;

		try {
			scanner = new Scanner(System.in);
			int[] numbers = { 12, 3, 4, 5 };

			int number = numbers[21];

		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			System.out.println("Before Scanner Close");
			if(scanner!=null) {
				scanner.close();
			}
		}
		
		System.out.println("Just before closing out main");
	}

}

/16-ExceptionHandling/src/com/in28minutes/exceptionhandling/ThrowingExceptionRunner.java

package com.in28minutes.exceptionhandling;

class Amount {
	private String currency;
	private int amount;
	
	public Amount(String currency, int amount) {
		super();
		this.currency = currency;
		this.amount = amount;
	}
	
	public void add(Amount that) throws CurrenciesDoNotMatchException {
		
		if(!this.currency.equals(that.currency)) {
			//throw new Exception("Currencies Don't Match " + this.currency + " & " +that.currency );
			throw new CurrenciesDoNotMatchException("Currencies Don't Match " + this.currency + " & " +that.currency );
		}
		
		this.amount = this.amount + that.amount;
	}
	
	public String toString() {
		return amount + " " + currency; 
	}
}

class CurrenciesDoNotMatchException extends Exception {
	public CurrenciesDoNotMatchException(String msg) {
		super(msg);
	}
}

public class ThrowingExceptionRunner {

	public static void main(String[] args) throws CurrenciesDoNotMatchException {
		Amount amount1 = new Amount("USD", 10);
		Amount amount2 = new Amount("EUR", 20);
		amount1.add(amount2);
		System.out.println(amount1);	
	}

}

/16-ExceptionHandling/src/com/in28minutes/exceptionhandling/TryWithResourcesRunner.java

package com.in28minutes.exceptionhandling;

import java.util.Scanner;

public class TryWithResourcesRunner {

	public static void main(String[] args) {
		try (Scanner scanner = new Scanner(System.in)) {
			int[] numbers = { 12, 3, 4, 5 };
			int number = numbers[21];
		} 
	}

}

17-Files

Steps

Step 01 - List files and folders in Directory with Files list method
Step 02 - Recursively List and Filter all files and folders in Directory with Step Files walk method and Search with find method
Step 03 - Read content from a File - Files readAllLines and lines methods
Step 04 - Writing Content to a File - Files write method
Step 05 - Files - Conclusion

Code Examples

/17-Files/src/files/DirectoryScanRunner.java

package files;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.function.BiPredicate;
import java.util.function.Predicate;

public class DirectoryScanRunner {

	public static void main(String[] args) throws IOException {
		
		Path currentDirectory = Paths.get(".");
		//Files.list(currentDirectory).forEach(System.out::println);
		
		Predicate<? super Path> predicate 
				= path -> String.valueOf(path).contains(".java");
		
		//Files.walk(currentDirectory, 4).filter(predicate).forEach(System.out::println);
		
		BiPredicate<Path, BasicFileAttributes> javaMatcher 
		= (path,attributes) -> String.valueOf(path).contains(".java");

		BiPredicate<Path, BasicFileAttributes> directoryMatcher 
		= (path,attributes) -> attributes.isDirectory();

		
		Files.find(currentDirectory, 4, directoryMatcher )
							.forEach(System.out::println);
		     
	}

}

/17-Files/src/files/FileReadRunner.java

package files;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;

public class FileReadRunner {

	public static void main(String[] args) throws IOException {
		Path pathFileToRead = Paths.get("./resources/data.txt");
		
		//List<String> lines = Files.readAllLines(pathFileToRead);
		//System.out.println(lines);
		
		Files.lines(pathFileToRead)
			.map(String::toLowerCase)
			.filter(str -> str.contains("a"))
			.forEach(System.out::println);
		
	}

}

/17-Files/src/files/FileWriteRunner.java

package files;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;

public class FileWriteRunner {

	public static void main(String[] args) throws IOException {
		Path pathFileToWrite = Paths.get("./resources/file-write.txt");
		
		List<String> list = 
					List.of("Apple", "Boy", "Cat", "Dog", "Elephant");
		
		Files.write(pathFileToWrite, list);
	
		
	}

}

/17-Files/resources/data.txt

123,122
jljlfsadf
Apple
Bat
Cat

/17-Files/resources/file-write.txt

Apple
Boy
Cat
Dog
Elephant

18-ConcurrencyLocksAtomicityAndCollections

Steps

Step 01 - Getting started with Synchronized
Step 02 - Problem with Synchronized - Less Concurrency
Step 03 - Enter Locks with ReEntrantLock
Step 04 - Introduction to Atomic Classes - AtomicInteger
Step 05 - Need for ConcurrentMap
Step 06 - Implementing an example with ConcurrentHashMap
Step 07 - ConcurrentHashMap uses different locks for diferrent regions
Step 08 - CopyOnWrite Concurrent Collections - When reads are more than writes
Step 09 - Conclusion

Code Examples

/src/com/in28minutes/concurrency/BiCounter.java

package com.in28minutes.concurrency;

public class BiCounter {
  private int i = 0;
  private int j = 0;
  
  synchronized public void incrementI() {
    i++; 
    //get i
    //increment  
    //set i
  }

  public int getI() {
    return i;
  }
  
  synchronized public void incrementJ() {
    j++; 
    //get j
    //increment  
    //set j
  }

  public int getJ() {
    return j;
  }

}

/src/com/in28minutes/concurrency/BiCounterWithAtomicInteger.java

package com.in28minutes.concurrency;

import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class BiCounterWithAtomicInteger {
  private AtomicInteger i = new AtomicInteger();
  private AtomicInteger j = new AtomicInteger();
    
  public void incrementI() {    
    i.incrementAndGet();
  }

  public int getI() {
    return i.get();
  }
  
  public void incrementJ() {
    j.incrementAndGet(); 
  }

  public int getJ() {
    return j.get();
  }

}

/src/com/in28minutes/concurrency/BiCounterWithLock.java

package com.in28minutes.concurrency;

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class BiCounterWithLock {
  private int i = 0;
  private int j = 0;
  
  Lock lockForI = new ReentrantLock();
  Lock lockForJ = new ReentrantLock();
  
  public void incrementI() {    
    lockForI.lock();//Get Lock For I 
    i++;
    lockForI.unlock();
    //Release Lock For I
  }

  public int getI() {
    return i;
  }
  
  public void incrementJ() {
    lockForJ.lock();//Get Lock For J
    j++; 
    lockForJ.unlock();//Release Lock For J
  }

  public int getJ() {
    return j;
  }

}

/src/com/in28minutes/concurrency/ConcurrencyRunner.java

package com.in28minutes.concurrency;

public class ConcurrencyRunner {

  public static void main(String[] args) {
    Counter counter = new Counter();
    counter.increment();
    counter.increment();
    counter.increment();
    System.out.println(counter.getI());

  }

}

/src/com/in28minutes/concurrency/ConcurrentMapRunner.java

package com.in28minutes.concurrency;

import java.util.Hashtable;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.atomic.LongAdder;

public class ConcurrentMapRunner {

  public static void main(String[] args) {
    ConcurrentMap<Character, LongAdder> occurances = new ConcurrentHashMap<>();
    
    String str = "ABCD ABCD ABCD";

    for(char character:str.toCharArray()) {
      occurances.computeIfAbsent(character, ch -> new LongAdder()).increment();
    }
    
    System.out.println(occurances);
        

  }

  /*
      Map<Character, LongAdder> occurances = new Hashtable<>();
    
    String str = "ABCD ABCD ABCD";
    for(char character:str.toCharArray()) {
      LongAdder longAdder = occurances.get(character);
      if(longAdder == null) {
        longAdder = new LongAdder();
      }
      longAdder.increment();
      occurances.put(character, longAdder);
    }
    
    System.out.println(occurances);

   */
}

/src/com/in28minutes/concurrency/CopyOnWriteArrayListRunner.java

package com.in28minutes.concurrency;

import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;

public class CopyOnWriteArrayListRunner {
  
  //add - copy
  //get

  public static void main(String[] args) {
    List<String> list = new CopyOnWriteArrayList<>();
    
    //Threads - 3
    list.add("Ant");
    list.add("Bat");
    list.add("Cat");
    
    //Threads - 10000
    for(String element:list) {
      System.out.println(element);
    }
    
    // TODO Auto-generated method stub

  }

}

/src/com/in28minutes/concurrency/Counter.java

package com.in28minutes.concurrency;

public class Counter {
  private int i = 0;
  
  synchronized public void increment() {
    i++; 
    //get i
    //increment  
    //set i
  }

  public int getI() {
    return i;
  }
}

99-TipsAndTricks

Steps

Java Tip 01 - Imports and Static Imports
Java Tip 02 - Blocks
Java Tip 03 - equals method
Java Tip 04 - hashcode method
Java Tip 05 - Class Access Modifiers - public and default
Java Tip 06 - Method Access Modifiers - public, protected, private and default
Java Tip 07 - Final classes and Final methods
Java Tip 08 - Final Variables and Final Arguments
Java Tip 09 - Why do we need static variables?
Java Tip 09 - Why do we need static methods?
Java Tip 10 - Static methods cannot use instance methods or variables
Java Tip 11 - public static final - Constants
Java Tip 12 - Nested Classes - Inner Class vs Static Nested Class
Java Tip 13 - Anonymous Classes
Java Tip 14 - Why Enum and Enum Basics - ordinal and values
Java Tip 15 - Enum - Constructor, variables and methods
Java Tip 16 - Quick look at inbuild Enums - Month, DayOfWeek

Code Examples

/src/com/in28minutes/tips/access/package1/ClassAccessModifiers.java

package com.in28minutes.tips.access.package1;


//public, protected, (default), private
public class ClassAccessModifiers {

  public static void main(String[] args) {
    // TODO Auto-generated method stub
    ClassAccessModifiers c = new ClassAccessModifiers();

  }

}

/src/com/in28minutes/tips/access/package1/ExampleClass.java

package com.in28minutes.tips.access.package1;

public class ExampleClass {
  public void publicMethod() {}
  protected void protectedMethod() {}
  private void privateMethod() {}
  void defaultMethod() {}
  
  public static void main(String[] args) {
    ExampleClass exampleClass = new ExampleClass();
    exampleClass.privateMethod();
    exampleClass.protectedMethod();
    exampleClass.publicMethod();
    exampleClass.defaultMethod();
  }
}

/src/com/in28minutes/tips/access/package1/MethodAccessRunnerInsideSamePackage.java

package com.in28minutes.tips.access.package1;

public class MethodAccessRunnerInsideSamePackage {

  public static void main(String[] args) {
    // TODO Auto-generated method stub
    ExampleClass exampleClass = new ExampleClass();
    //exampleClass.privateMethod();
    exampleClass.protectedMethod();
    exampleClass.publicMethod();
    exampleClass.defaultMethod();

  }

}

/src/com/in28minutes/tips/access/package2/ClassAccessModifiersRunnerInOtherPackage.java

package com.in28minutes.tips.access.package2;

import com.in28minutes.tips.access.package1.ClassAccessModifiers;

//public, protected, (default), private
public class ClassAccessModifiersRunnerInOtherPackage {

  public static void main(String[] args) {
    ClassAccessModifiers c = new ClassAccessModifiers();
  }

}

/src/com/in28minutes/tips/access/package2/MethodAccessRunnerInDifferentPackage.java

package com.in28minutes.tips.access.package2;

import com.in28minutes.tips.access.package1.ExampleClass;

public class MethodAccessRunnerInDifferentPackage {

  public static void main(String[] args) {
    // TODO Auto-generated method stub
    ExampleClass exampleClass = new ExampleClass();

    //exampleClass.privateMethod();
    //exampleClass.protectedMethod();
    exampleClass.publicMethod();
    //exampleClass.defaultMethod();

  }

}

/src/com/in28minutes/tips/anonymous/AnonymousClassRunner.java

package com.in28minutes.tips.anonymous;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

public class AnonymousClassRunner {
  
  public static void main(String[] args) {
    List<String> animals = new ArrayList<String>(
        List.of("Ant", "Cat", "Ball", "Elephant"));
    
    Comparator<String> lengthComparator = new Comparator<String>() {
      @Override
      public int compare(String str1, String str2) {
        return Integer.compare(str1.length(), str2.length());
      }
    };
    
    Collections.sort(animals, 
        lengthComparator
    );
    System.out.println(animals);

  }

}

/src/com/in28minutes/tips/blocks/BlocksRunner.java

package com.in28minutes.tips.blocks;

public class BlocksRunner {
  public static final int SECONDS_IN_MINUTE = 60;
  public static final int MINUTES_IN_HOUR = 60;
  public static final int HOURS_IN_DAY = 24;
  public static final int SECONDS_IN_DAY 
    = SECONDS_IN_MINUTE * MINUTES_IN_HOUR * HOURS_IN_DAY;
  
  public static void main(String[] args) {
    //System.out.print(Integer.MIN_VALUE);
    System.out.print(SECONDS_IN_DAY);
    
    //System.out.print("main");
    
    {
      int i;
      //System.out.print("3>2");
        //System.out.print("3>2");
    }
    
    //System.out.print(i); 

  }

}

/src/com/in28minutes/tips/eclipse/DummyForTest.java

package com.in28minutes.tips.eclipse;

import java.util.ArrayList;
import java.util.List;

public class DummyForTest {

  public void doSomething() {
    List list = new ArrayList();
  }

}

/src/com/in28minutes/tips/eclipse/EclipseTipsAndTricks.java

package com.in28minutes.tips.eclipse;

import java.math.BigDecimal;

//PAIR PROGRAMMING

class TestBean {
  private int i; //i is awesome
  private String str;
  
  
  
  public TestBean() {
    /*
     fsadjflkas
     fskljdfalsk
     */
    super();  
  }
  
  public TestBean(int i, String str) {
    super();
    this.i = i;
    this.str = str;
  }
  /* (non-Javadoc)
   * @see java.lang.Object#hashCode()
   */
  @Override
  public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result + i;
    return result;
  }
  /* (non-Javadoc)
   * @see java.lang.Object#equals(java.lang.Object)
   */
  @Override
  public boolean equals(Object obj) {
    if (this == obj) {
      return true;
    }
    if (obj == null) {
      return false;
    }
    if (getClass() != obj.getClass()) {
      return false;
    }
    TestBean other = (TestBean) obj;
    if (i != other.i) {
      return false;
    }
    return true;
  }
  /**
   * @return the i
   */
  public int getI() {
    return i;
  }
  /**
   * @param i the i to set
   */
  public void setI(int i) {
    this.i = i;
  }
  /**
   * @return the str
   */
  public String getStr() {
    return str;
  }
  /**
   * @param str the str to set
   */
  public void setStr(String str) {
    this.str = str;
  }
  
  
  
}

class Test implements Comparable<String> {

  @Override
  public int compareTo(String arg0) {
    return 0;
  }
  
}

public class EclipseTipsAndTricks {
  
  public static void main(String[] args) throws InterruptedException {
    
    DummyForTest dt = new DummyForTest();
    dt.doSomething();
    BigDecimal bd = new BigDecimal(25);
    Thread.sleep(returnSomething());
  }

  private static int returnSomething() {
    return 1000 * 45 * 456;
  }

}

/src/com/in28minutes/tips/enums/EnumRunner.java

package com.in28minutes.tips.enums;

import java.util.Arrays;

public class EnumRunner {

  public static void main(String[] args) {
    Season season = Season.FALL;

    Season season1 = Season.valueOf("WINTER");
    System.out.println(season1);
    System.out.println(Season.SPRING.ordinal());
    System.out.println(Season.SPRING.getValue());

    System.out
        .println(Arrays.toString(Season.values()));

  }

}

/src/com/in28minutes/tips/enums/Season.java

package com.in28minutes.tips.enums;
public enum Season {
  SPRING(4), SUMMER(1), WINTER(2), FALL(3) ;
  
  private int value;
  
  private Season(int value) {
    this.value = value;
  }

  public int getValue() {
    return value;
  }
  
  
  //0,1,2,3
}

/src/com/in28minutes/tips/equals/EqualsRunner.java

package com.in28minutes.tips.equals;

class Client {
  private int id;

  public Client(int id) {
    super();
    this.id = id;
  }

  @Override
  public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result + id;
    return result;
  }

  @Override
  public boolean equals(Object that) {
    if (this == that)
      return true;
    
    if (that == null)
      return false;
    if (getClass() != that.getClass())
      return false;
    Client other = (Client) that;
    if (id != other.id)
      return false;
    return true;
  }
  
  //equals
  //hashcode
  
  
  
}

public class EqualsRunner {

  public static void main(String[] args) {
    Client c1 = new Client(1);
    Client c2 = new Client(1);
    Client c3 = new Client(2);
    System.out.println(c1.equals(c2));
    System.out.println(c1.equals(c3));
    
    
  }

}

/src/com/in28minutes/tips/imports/ImportsRunner.java

package com.in28minutes.tips.imports;

//import java.lang.*; //DEFAULT
import java.math.BigDecimal;
import java.util.ArrayList;
//import java.util.Collections;

import static java.lang.System.out;
import static java.util.Collections.*;

public class ImportsRunner {

  public static void main(String[] args) {
    
    out.println("IMports");
    out.println("Static Imports");
    
    sort(new ArrayList<String>());
    
    BigDecimal db = null;

  }

}

/src/com/in28minutes/tips/nonaccess/package1/FinalNonAccessModifierRunner.java

package com.in28minutes.tips.nonaccess.package1;

final class FinalClass {
  
}

//class SomeClass extends FinalClass{
//}

class SomeClass {
  final public void doSomething() {}
  public void doSomethingElse(final int arg) {
    //arg = 6;
    
  }
}

class ExtendingClass extends SomeClass {
  //public void doSomething() {}
}

public class FinalNonAccessModifierRunner {
  
  public static void main(String[] args) {
    final int i;
    i=5;
    
    //i = 7;

  }

}

/src/com/in28minutes/tips/nonaccess/package1/StaticModifierRunner.java

package com.in28minutes.tips.nonaccess.package1;

class Player{
  private String name;
  
  private static int count = 0;
  
  public Player(String name) {
    super();
    this.name = name;
    count++;
  }

  static public int getCount() {
    return count;
  }

  public String getName() {
    System.out.println(count);
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }
  
  
}

public class StaticModifierRunner {
  
  public static void main(String[] args) {
    Player player1 = new Player("Ronaldo");
    
    System.out.println(Player.getCount());
    
    Player player2 = new Player("Federer");
    
    System.out.println(Player.getCount());
  }

}

Files

00-01-course-guide.md

Latest commit

History

00-01-course-guide.md

File metadata and controls

Course Guide

01-IntroductionToJavaProgrammingWithJShell

Steps

Exercises

Expressions

Printing Output to Console

Advanced Printing Output to Console

Variables

If Statement

For Loop

Code Snippets

02-IntroductionToMethods-MultiplicationTable

Steps

Exercises

Methods - Basics

Method Parameters

Return value from Methods

Code Snippets

03-IntroductionToJavaPlatform

Steps

Code Snippets (Including Output)

/03-IntroductionToJavaPlatform/Planet.java

04-IntroductionToEclipse-FirstJavaProject

Steps

Code Examples

/04-IntroductionToEclipse-FirstJavaProject/src/com/in28minutes/firstjavaproject/HelloWorld.java

/04-IntroductionToEclipse-FirstJavaProject/src/com/in28minutes/firstjavaproject/KeyboardShortcuts.java

/04-IntroductionToEclipse-FirstJavaProject/src/com/in28minutes/firstjavaproject/MultiplicationTable.java

/04-IntroductionToEclipse-FirstJavaProject/src/com/in28minutes/firstjavaproject/MultiplicationTableRunner.java

/04-IntroductionToEclipse-FirstJavaProject/src/com/in28minutes/firstjavaproject/MutliplicationTableBeforeRefactoring.java

05-IntroductionToObjectOrientedProgramming

Steps

Exercises

Code Examples

/05-IntroductionToObjectOrientedProgramming/src/com/in28minutes/oops/Book.java

/05-IntroductionToObjectOrientedProgramming/src/com/in28minutes/oops/BookRunner.java

/05-IntroductionToObjectOrientedProgramming/src/com/in28minutes/oops/MotorBike.java

/05-IntroductionToObjectOrientedProgramming/src/com/in28minutes/oops/MotorBikeRunner.java

/05-IntroductionToObjectOrientedProgramming/entireoutput-constructor-puzzles.txt

06-PrimitiveDataTypesAndAlternatives

Steps

Exercises

Big Decimal

char data type

Code Examples

/06-PrimitiveDataTypesAndAlternatives/commands.txt

/06-PrimitiveDataTypesAndAlternatives/src/com/in28minutes/primitive/datatypes/BiNumber.java

/06-PrimitiveDataTypesAndAlternatives/src/com/in28minutes/primitive/datatypes/BiNumberRunner.java

/06-PrimitiveDataTypesAndAlternatives/src/com/in28minutes/primitive/datatypes/MyChar.java

/06-PrimitiveDataTypesAndAlternatives/src/com/in28minutes/primitive/datatypes/MyCharRunner.java

/06-PrimitiveDataTypesAndAlternatives/src/com/in28minutes/primitive/datatypes/SimpleInterestCalculator.java

/06-PrimitiveDataTypesAndAlternatives/src/com/in28minutes/primitive/datatypes/SimpleInterestCalculatorRunner.java

07-Conditionals

Steps

Exercises

If and Nested If Else - Design a Menu

Switch

Code Examples

/07-Conditionals/commands.txt

/07-Conditionals/src/com/in28minutes/ifstatement/examples/IfStatementRunner.java

/07-Conditionals/src/com/in28minutes/ifstatement/examples/MenuRunner.java

/07-Conditionals/src/com/in28minutes/ifstatement/examples/SwitchExercisesRunner.java

/07-Conditionals/src/com/in28minutes/ifstatement/examples/SwitchStatementRunner.java

08-Loops

Steps

Exercises

For Loop

While

Choosing Loops

Code Examples

/08-Loops/commands.txt

/08-Loops/src/com/in28minutes/loops/DoWhileRepeatedQuestionRunner.java

/08-Loops/src/com/in28minutes/loops/MyNumber.java

/08-Loops/src/com/in28minutes/loops/MyNumberRunner.java