加不加Volatile看不出有啥效果啊?

import java.util.concurrent.atomic.AtomicInteger;public class VolatilePattern1 extends Thread{volatile boolean shutdownRequested;private AtomicInteger count = new AtomicInteger();public void shutdown() {shutdownRequested = true;}public void run() { System.out.println("Thread:" + Thread.currentThread().getName()+" started.");    while (!shutdownRequested) {         System.out.println("working ..."+count);        count.getAndIncrement();        try {Thread.sleep(50);} catch(InterruptedException ie) {ie.printStackTrace();}    }}public static void main(String[] args) {System.out.println("Thread:" + Thread.currentThread().getName()+" started.");VolatilePattern1 vp = new VolatilePattern1();vp.start();try {Thread.sleep(2000);} catch(InterruptedException ie) {ie.printStackTrace();} finally {vp.shutdown();}}}