Thread Safe Demos

StringBufferVsStringBuilder.java

import java.util.Random;

public class StringBufferVsStringBuilder {
	public static int demo(final Object stringJoiner, final int testCount) throws InterruptedException {
		ThreadGroup group = new ThreadGroup(stringJoiner.getClass().getName() + "@" + stringJoiner.hashCode()); 
		final Random rand = new Random(); 
		
		Runnable listAppender = new Runnable() {
			public void run() {
				try {
					Thread.sleep(rand.nextInt(2));
				} catch (InterruptedException e) {
					return; 
				} 
				if (stringJoiner instanceof StringBuffer) {
					((StringBuffer)stringJoiner).append("0");
				} else if (stringJoiner instanceof StringBuilder) {
					((StringBuilder)stringJoiner).append("0"); 
				}
			}
		}; 
		
		for (int i = 0; i < testCount; i++) {
			new Thread(group, listAppender, "InsertList-" + i).start(); 
		}
		
		while (group.activeCount() > 0) {
			Thread.sleep(10); 
		}
		
		return stringJoiner.toString().length(); 
	}
	
	public static void main(String[] args) throws InterruptedException {
		StringBuilder stringBuilder = new StringBuilder();
		StringBuffer stringBuffer = new StringBuffer();
		final int N = 10000; 
		for (int i = 0; i < 10; i++) {
			stringBuilder.delete(0, stringBuilder.length()); 
			stringBuffer.delete(0, stringBuffer.length()); 
			int builderLength = demo(stringBuilder, N); 
			int bufferLength = demo(stringBuffer, N); 
			System.out.println("StringBuilder/StringBuffer: " + builderLength + "/" + bufferLength); 
		}
	}
}


// Output will be something like this:
// StringBuilder/StringBuffer: 9995/10000
// StringBuilder/StringBuffer: 9996/10000
// StringBuilder/StringBuffer: 9998/10000
// StringBuilder/StringBuffer: 9997/10000
// StringBuilder/StringBuffer: 9995/10000
// StringBuilder/StringBuffer: 9996/10000
// StringBuilder/StringBuffer: 9998/10000
// StringBuilder/StringBuffer: 9998/10000
// StringBuilder/StringBuffer: 9999/10000
// StringBuilder/StringBuffer: 9999/10000

ThreadSafeDemo.java

package com.ibm.javacore.collections.threadsafe;

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

public class ThreadSafeDemo {
	public static int demo(final List list, final int testCount) throws InterruptedException {
		ThreadGroup group = new ThreadGroup(list.getClass().getName() + "@" + list.hashCode()); 
		final Random rand = new Random(); 
		
		Runnable listAppender = new Runnable() {
			public void run() {
				try {
					Thread.sleep(rand.nextInt(2));
				} catch (InterruptedException e) {
					return; 
				} 
				list.add("0"); 
			}
		}; 
		
		for (int i = 0; i < testCount; i++) {
			new Thread(group, listAppender, "InsertList-" + i).start(); 
		}
		
		while (group.activeCount() > 0) {
			Thread.sleep(10); 
		}
		
		return list.size(); 
	}
	public static void main(String[] args) throws InterruptedException {
		List unsafeList = new ArrayList(); 
		List safeList = Collections.synchronizedList(new ArrayList()); 
		final int N = 10000; 
		for (int i = 0; i < 10; i++) {
			unsafeList.clear(); 
			safeList.clear(); 
			int unsafeSize = demo(unsafeList, N); 
			int safeSize = demo(safeList, N); 
			System.out.println("unsafe/safe: " + unsafeSize + "/" + safeSize); 
		}
	}
}

// Output will be something like this:
// unsafe/safe: 9999/10000
// unsafe/safe: 9997/10000
// unsafe/safe: 10000/10000
// unsafe/safe: 10000/10000
// unsafe/safe: 9999/10000
// unsafe/safe: 9999/10000
// unsafe/safe: 10000/10000
// unsafe/safe: 9998/10000
// unsafe/safe: 10000/10000
// unsafe/safe: 10000/10000