Java Program to implement hash tables.java

/**
 * Java program to implement Hash Table
 **/
 
import java.util.Scanner;
 
class HashTable
{
    int[] arr;
    int capacity;
 
    /** constructor **/
    public HashTable(int capacity)
    {
        this.capacity = nextPrime(capacity);
        arr = new int[this.capacity];
    }
 
    /** function to insert **/
    public void insert(int ele)
    {
        arr[ele % capacity] = ele;
    }
 
    /** function to clear **/
    public void clear()
    {
        arr = new int[capacity];
    }
 
    /** function contains **/
    public boolean contains(int ele)
    {
        return arr[ele % capacity] == ele;
    }
 
    /** function to delete **/
    public void delete(int ele)
    {
        if (arr[ele % capacity] == ele)
            arr[ele % capacity] = 0;
        else
            System.out.println("\nError : Element not found\n");
    }
 
    /** Function to generate next prime number >= n **/
    private static int nextPrime( int n )
    {
        if (n % 2 == 0)
            n++;
        for (; !isPrime(n); n += 2);
 
        return n;
    }
 
    /** Function to check if given number is prime **/
    private static boolean isPrime(int n)
    {
        if (n == 2 || n == 3)
            return true;
        if (n == 1 || n % 2 == 0)
            return false;
        for (int i = 3; i * i <= n; i += 2)
            if (n % i == 0)
                return false;
        return true;
    }
 
    /** function to print hash table **/
    public void printTable()
    {
        System.out.print("\nHash Table = ");
        for (int i = 0; i < capacity; i++)
            System.out.print(arr[i] +" ");
        System.out.println();
    }
}
 
/** Class HashTableTest **/
public class HashTableTest
{
    public static void main(String[] args)
    {
        Scanner scan = new Scanner(System.in);
        System.out.println("Hash Table Test\n\n");
        System.out.println("Enter size");
        /** Make object of HashTable **/
        HashTable ht = new HashTable(scan.nextInt() );
 
        char ch;
        /**  Perform HashTable operations  **/
        do    
        {
            System.out.println("\nHash Table Operations\n");
            System.out.println("1. insert ");
            System.out.println("2. remove");
            System.out.println("3. contains");            
            System.out.println("4. clear");            
 
            int choice = scan.nextInt();            
            switch (choice)
            {
            case 1 : 
                System.out.println("Enter integer element to insert");
                ht.insert( scan.nextInt() ); 
                break;                          
            case 2 :                 
                System.out.println("Enter integer element to delete");
                ht.delete( scan.nextInt() ); 
                break;                        
            case 3 : 
                System.out.println("Enter integer element to check if present");
                System.out.println("Contains : "+ ht.contains(scan.nextInt() ));
                break;                                   
            case 4 : 
                ht.clear();
                System.out.println("Hash Table Cleared\n");
                break;
            default : 
                System.out.println("Wrong Entry \n ");
                break;   
            }
            /** Display hash table **/
            ht.printTable();  
 
            System.out.println("\nDo you want to continue (Type y or n) \n");
            ch = scan.next().charAt(0);                        
        } while (ch == 'Y'|| ch == 'y');  
    }
}