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java 等待线程/线程池执行完毕

2017-08-07 15:43 417 查看

1.单线程开始并执行完毕

当线程开始后，需要用到join的方法

不废话直接贴代码

public static void main(String args[]) {
long begin = System.currentTimeMillis();
System.out.println(begin);
Thread thread = new Thread(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(1000L);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("111");
}
});
try {
thread.start();
thread.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
long end = System.currentTimeMillis();
System.out.println(end-begin);
System.out.println("执行完毕");
}

运行结果：

1502091332017
111
1002
执行完毕

现在我们来看一下join这个方法

/**
* Waits for this thread to die.
*
* <p> An invocation of this method behaves in exactly the same
* way as the invocation
*
* <blockquote>
* {@linkplain #join(long) join}{@code (0)}
* </blockquote>
*
* @throws  InterruptedException
*          if any thread has interrupted the current thread. The
*          <i>interrupted status</i> of the current thread is
*          cleared when this exception is thrown.
*/
public final void join() throws InterruptedException {
join(0);
}
翻译为中文大意就是，等待线程执行完毕！

2.等待线程池执行完毕

等待线程池执行完毕我们需要用到

CountDownLatch这个类

且看代码：

public static void main(String args[]) throws InterruptedException {
final CountDownLatch count = new CountDownLatch(3);
ExecutorService fixedThreadPool = Executors.newFixedThreadPool(3);
try {
long begin = System.currentTimeMillis();
System.out.println(begin);
fixedThreadPool.execute(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(1000L);
count.countDown();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("111");
}
});
fixedThreadPool.execute(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(2000L);
count.countDown();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("222");
}
});
fixedThreadPool.execute(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(3000L);
count.countDown();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("333");
}
});

count.await();
long end = System.currentTimeMillis();
System.out.println(end-begin);
System.out.println("执行完毕");
} finally {
fixedThreadPool.shutdown();
}
}

最后一定要记得线程池关闭，要不会出大问题的

运行结果：

1502091739441
111
222
333
3002
执行完毕

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标签： java 线程池线程执行完毕

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