比如，主线程创建线程池，提交n个任务，想让主线程在任务全部结束之后再继续做其他的事情。
1、使用awaitTermination方法
public static void main(String[] args) { ExecutorService executor = Executors.newFixedThreadPool(3); int i = 0; AtomicInteger result = new AtomicInteger(0); while (i < 10) { i++; executor.execute(() -> { //每执行一次，对result加1 System.out.println(result.addAndGet(1)); }); } System.out.println("调用shutdown()方法时，result的值为：" + result.get()); executor.shutdown(); try { //等待所有任务结束，最多等待30分钟 executor.awaitTermination(30, TimeUnit.MINUTES); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("计算完成，result的值为：" + result.get() + "，可以继续处理其他事情了"); } boolean awaitTermination(long timeout, TimeUnit unit)的作用：
Blocks until all tasks have completed execution after a shutdown request,
or the timeout occurs, or the current thread is interrupted,
whichever happens first.
2、借助工具类CountDownLatch
public static void main(String[] args) { ExecutorService executor = Executors.newFixedThreadPool(3); CountDownLatch latch = new CountDownLatch(10); AtomicInteger result = new AtomicInteger(0); for (int i = 1; i <= 10; i++) { executor.execute(() -> { //do something... System.out.println(result.addAndGet(1)); //then latch.countDown(); }); } System.out.println("调用shutdown()方法时，result的值为：" + result.get()); executor.shutdown(); try { latch.await();//等待任务结束：其实是等待latch值为0 } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("计算完成，result的值为：" + result.get() + "，可以继续处理其他事情了"); } 适用于知道任务的数量，因为CountDownLatch在创建时就要指定其大小，并且不能重新初始化。
//TODO：CountDownLatch是否会禁止指令重排序？(从官方的例子看，会！有待研究)
public void example() { CountDownLatch doneSignal = new CountDownLatch(10); Executor e = Executors.newFixedThreadPool(10); for (int i = 0; i < 10; ++i) // create and start threads e.execute(new WorkerRunnable(doneSignal, i)); try { doneSignal.await(); // wait for all to finis } catch (InterruptedException e1) { e1.printStackTrace(); } } class WorkerRunnable implements Runnable { private final CountDownLatch doneSignal; private final int i; WorkerRunnable(CountDownLatch doneSignal, int i) { this.doneSignal = doneSignal; this.i = i; } public void run() { doWork(i); doneSignal.countDown(); } void doWork(int i) { } } 其他
//TODO
作者：maxwellyue
链接：https://www.jianshu.com/p/bcbfb58d0da5
来源：简书
简书著作权归作者所有，任何形式的转载都请联系作者获得授权并注明出处。