Question

我有一个新手问题。我有这段代码：

public class Main 
{

    public static void main(String[] args) throws InterruptedException 
    {
        // TODO Auto-generated method stub
        IntHolder aHolder=new IntHolder();
        aHolder.Number=0;

        IncrementorThread A= new IncrementorThread(1, aHolder);
        IncrementorThread B= new IncrementorThread(2, aHolder);
        IncrementorThread C= new IncrementorThread(3, aHolder);

        A.start();
        B.start();
        C.start();

        A.join();
        B.join();
        C.join();
        System.out.println("All threads completed...");

    }

}

将等待所有线程完成。如果我像这样使用Executors：

public class Main 
{

    public static void main(String[] args) 
    {
        // TODO Auto-generated method stub
        IntHolder aHolder=new IntHolder();
        aHolder.number=0;

        IncrementalRunable A= new IncrementalRunable(1, aHolder);
        IncrementalRunable B= new IncrementalRunable(2, aHolder);
        IncrementalRunable C= new IncrementalRunable(3, aHolder);

        ExecutorService exec = Executors.newFixedThreadPool(3);
        exec.execute(A);
        exec.execute(B);
        exec.execute(C);
        //Don't know what to do here

        System.out.println("All threads completed...");
    }
}

如何暂停主线程以等待执行程序中的所有线程完成，即在所有线程完成工作后应打印“所有线程已完成...”？

Answer 1

如果您想等待任务完成，则不应使用此类执行程序。如果您不希望/无法关闭线程池执行程序，该怎么办？这是一种更推荐的方式：

    ExecutorService exec = Executors.newFixedThreadPool(3);
    Collection<Future<?>> tasks = new LinkedList<Future<?>>();

    Future<T> future = exec.submit(A);
    tasks.add(future);
    future = exec.submit(B);
    tasks.add(future);
    future = exec.submit(C);
    tasks.add(future);

    // wait for tasks completion
    for (Future<?> currTask : tasks) {
            try {
                currTask.get();
            } catch (Throwable thrown) {
                Logger.error(thrown, "Error while waiting for thread completion");
            }
        }

Answer 2

executor.shutdown();
while (!executor.awaitTermination(24L, TimeUnit.HOURS)) {
    System.out.println("Not yet. Still waiting for termination");
}

使用shutdown() + awaitTermination()组合。

修改的

基于@Lital的评论

List<Callable<Object>> calls = new ArrayList<Callable<Object>>(); calls.add(Executors.callable(new IncrementalRunable(1, aHolder))); calls.add(Executors.callable(new IncrementalRunable(2, aHolder))); calls.add(Executors.callable(new IncrementalRunable(3, aHolder))); List<Future<Object>> futures = executor.invokeAll(calls);

注意：在完成所有任务（通过失败或完成成功执行）之前，invokeAll()将不会返回。

Answer 3

我们可以使用下面的代码来加入线程。

 executor.execute(new YouThread());

    try{     
         executor.shutdown();
         while (!executor.awaitTermination(24L, TimeUnit.HOURS)) {
             System.out.println("Not yet. Still waiting for termination");
         }                
    }catch(InterruptedException e){
        e.printStackTrace();
    }

Answer 4

尝试以这种方式使用线程池。

executor.shutdown();
executor.awaitTermination(MAX_PRIORITY, TimeUnit.HOURS);

Answer 5

 exec.shutdown();
    // Wait until all threads are finish
    exec.awaitTermination();

执行者中的Thread.join（）等价物

5 个答案: