线程不安全代码测验
private static class UnsafeSequence { private int value; public int getNext() { return value++; } } 使用两个线程分别调用上面的getNext方法1000次，出现了一次线程不安全的情况，在转出的结果中有两个1311：
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原因剖析，与书上说的一致：
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完好的代码
import java.io.PrintWriter; import java.util.concurrent.CountDownLatch; / * Created by luohao07 on 2018/1/2. */ public class UnsafeSequenceTest { public static void main(String[] args) throws Exception{ UnsafeSequence unsafeSequence = new UnsafeSequence(); PrintWriter out = new PrintWriter(“out.txt”); CountDownLatch countDownLatch = new CountDownLatch(2); new Thread() { @Override public void run() { for (int i = 0; i < 1000; i++) { out.println(unsafeSequence.getNext() + " T1"); } countDownLatch.countDown(); } }.start(); new Thread() { @Override public void run() { for (int i = 0; i < 1000; i++) { out.println(unsafeSequence.getNext()+" T2"); } countDownLatch.countDown(); } }.start(); countDownLatch.await(); out.flush(); out.close(); } private static class UnsafeSequence { private int value; public int getNext() { return value++; } }} Timer执行定时使命
public class TimerTest { public static void main(String[] args) { Timer timer = new Timer(); timer.schedule(new TimerTask() { @Override public void run() { System.out.println(“invoke….”); } }, new Date(System.currentTimeMillis() + 5000)); }} 程序启动后5秒输出invoke….
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