StringTest.java

package lee;

import java.util.ArrayList;
import java.util.Random;

/**
 * java -server -Xms10G -Xmx10G -XX:+PrintGCDetails 
 * -XX:+UseConcMarkSweepGC -XX:CompileThreshold=1000 lee/StringTest
 * taskset -c 0-[0,1,3,7] java ...
 * @author CarpenterLee
 */
public class StringTest {

	public static void main(String[] args) {
		new StringTest().doTest();
	}
	public void doTest(){
		warmUp();
		int[] lengths = {
				10000, 
				100000, 
				1000000, 
				10000000, 
				20000000, 
				40000000
			};
		for(int length : lengths){
			System.out.println(String.format("---List length: %d---", length));
			ArrayList<String> list = randomStringList(length);
			int times = 4;
			String min1 = "1";
			String min2 = "2";
			String min3 = "3";
			long startTime;
			
			startTime = System.nanoTime();
			for(int i=0; i<times; i++){
				min1 = minStringForLoop(list);
			}
			TimeUtil.outTimeUs(startTime, "minStringForLoop time:", times);
			
			startTime = System.nanoTime();
			for(int i=0; i<times; i++){
				min2 = minStringStream(list);
			}
			TimeUtil.outTimeUs(startTime, "minStringStream time:", times);

			startTime = System.nanoTime();
			for(int i=0; i<times; i++){
				min3 = minStringParallelStream(list);	
			}
			TimeUtil.outTimeUs(startTime, "minStringParallelStream time:", times);
			
			System.out.println(min1.equals(min2) && min2.equals(min3));
//			System.out.println(min1);
		}
	}
	private void warmUp(){
		ArrayList<String> list = randomStringList(10);
		for(int i=0; i<20000; i++){
			minStringForLoop(list);
			minStringStream(list);
			minStringParallelStream(list);
			
		}
	}
	private String minStringForLoop(ArrayList<String> list){
		String minStr = null;
		boolean first = true;
		for(String str : list){
			if(first){
				first = false;
				minStr = str;
			}
			if(minStr.compareTo(str)>0){
				minStr = str;
			}
		}
		return minStr;
	}
	private String minStringStream(ArrayList<String> list){
		return list.stream().min(String::compareTo).get();
	}
	private String minStringParallelStream(ArrayList<String> list){
		return list.stream().parallel().min(String::compareTo).get();
	}
	private ArrayList<String> randomStringList(int listLength){
		ArrayList<String> list = new ArrayList<>(listLength);
		Random rand = new Random();
		int strLength = 10;
		StringBuilder buf = new StringBuilder(strLength);
		for(int i=0; i<listLength; i++){
			buf.delete(0, buf.length());
			for(int j=0; j<strLength; j++){
				buf.append((char)('a'+rand.nextInt(26)));
			}
			list.add(buf.toString());
		}
		return list;
	}
}