Just for test the anti-volatile example, see http://ifeve.com/java-memory-model-1/

VolatileTest.java

package volatile_demo;

import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;

public class Test2 {
	
	int a = 0;
	int b = 0;
	
	int x = -1;
	int y = -1;
	
	public void path1(){
		a = 1;
		x = b;
	}
	
	public void path2(){
		b = 2;
		y = a;
	}
	
	public boolean test() throws InterruptedException {
		
		a = b = 0;
		x = y = -1;
		
		CyclicBarrier barrier = new CyclicBarrier(2);
		
		Thread t1 = new Thread(){
			public void run() {
				try {
					barrier.await();
					path1();
				} catch (InterruptedException | BrokenBarrierException e) {
				}
			};
		};
		Thread t2 = new Thread(){
			public void run() {
				try {
					barrier.await();
					path2();
				} catch (InterruptedException | BrokenBarrierException e) {
				}
			};
		};
		t1.start();
		t2.start();
		
		t1.join();
		t2.join();
		
		if(x == 0 && y == 0)
			return false;
		else return true;
	}
	
	
	public static void main(String[] args) throws InterruptedException {
		for(int i = 0; i< 100*1000; i++){
			if(new Test2().test()==false) {
				System.out.println("found on " + i);
			}
		}
	}
	

}