java併發編程實戰第一章

線程不安全代碼測試

private static class UnsafeSequence { private int value; public int getNext() { return value++; } } 

使用兩個線程分別調用上面的getNext方法1000次，出現了一次線程不安全的狀況，在轉出的結果中有兩個1311：

 

 

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緣由分析，與書上說的一致：

 

 

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完整的代碼

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執行定時任務

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)); } } 

程序啓動後5秒輸出invoke....