所以我把我的答案贴在这里，以防有人想要一个更简单的方法来做到这一点

ExecutorService executor = Executors.newFixedThreadPool(10);
CompletableFuture[] futures = new CompletableFuture[10];
int i = 0;
while (...) {
    futures[i++] =  CompletableFuture.runAsync(runner, executor);
}

CompletableFuture.allOf(futures).join(); // THis will wait until all future ready.

这可能会有所帮助

Log.i(LOG_TAG, "shutting down executor...");
executor.shutdown();
while (true) {
                try {
                    Log.i(LOG_TAG, "Waiting for executor to terminate...");
                    if (executor.isTerminated())
                        break;
                    if (executor.awaitTermination(5000, TimeUnit.MILLISECONDS)) {
                        break;
                    }
                } catch (InterruptedException ignored) {}
            }

只是在这里提供更多不同于使用闩锁/屏障的选择。 你也可以在它们全部使用完CompletionService之前得到部分结果。

来自Java并发实践: “如果您有一批计算要提交给Executor，并且您希望检索它们的结果 可用时，您可以保留与每个任务关联的Future，并通过调用get来重复轮询完成 超时为0。这是可能的，但很乏味。幸运的是，还有更好的方法:完井服务。”

这里是实现

public class TaskSubmiter {
    private final ExecutorService executor;
    TaskSubmiter(ExecutorService executor) { this.executor = executor; }
    void doSomethingLarge(AnySourceClass source) {
        final List<InterestedResult> info = doPartialAsyncProcess(source);
        CompletionService<PartialResult> completionService = new ExecutorCompletionService<PartialResult>(executor);
        for (final InterestedResult interestedResultItem : info)
            completionService.submit(new Callable<PartialResult>() {
                public PartialResult call() {
                    return InterestedResult.doAnOperationToGetPartialResult();
                }
        });

    try {
        for (int t = 0, n = info.size(); t < n; t++) {
            Future<PartialResult> f = completionService.take();
            PartialResult PartialResult = f.get();
            processThisSegment(PartialResult);
            }
        } 
        catch (InterruptedException e) {
            Thread.currentThread().interrupt();
        } 
        catch (ExecutionException e) {
            throw somethinghrowable(e.getCause());
        }
    }
}

在Java8中，你可以用CompletableFuture来实现:

ExecutorService es = Executors.newFixedThreadPool(4);
List<Runnable> tasks = getTasks();
CompletableFuture<?>[] futures = tasks.stream()
                               .map(task -> CompletableFuture.runAsync(task, es))
                               .toArray(CompletableFuture[]::new);
CompletableFuture.allOf(futures).join();    
es.shutdown();

你也可以使用期货列表:

List<Future> futures = new ArrayList<Future>();
// now add to it:
futures.add(executorInstance.submit(new Callable<Void>() {
  public Void call() throws IOException {
     // do something
    return null;
  }
}));

然后当你想要连接所有线程时，它本质上等同于连接每个线程，(额外的好处是它会从子线程重新引发异常到主线程):

for(Future f: this.futures) { f.get(); }

Basically the trick is to call .get() on each Future one at a time, instead of infinite looping calling isDone() on (all or each). So you're guaranteed to "move on" through and past this block as soon as the last thread finishes. The caveat is that since the .get() call re-raises exceptions, if one of the threads dies, you would raise from this possibly before the other threads have finished to completion [to avoid this, you could add a catch ExecutionException around the get call]. The other caveat is it keeps a reference to all threads so if they have thread local variables they won't get collected till after you get past this block (though you might be able to get around this, if it became a problem, by removing Future's off the ArrayList). If you wanted to know which Future "finishes first" you could use some something like https://stackoverflow.com/a/31885029/32453

Project Loom的AutoCloseable执行器服务上的Try-with-Resources语法

Project Loom试图为Java中的并发能力添加新特性。

其中一个特性是使ExecutorService可自动关闭。这意味着每个ExecutorService实现都将提供一个close方法。这意味着我们可以使用try-with-resources语法自动关闭ExecutorService对象。

executorservice# close方法将阻塞，直到所有提交的任务都完成。使用close代替了调用shutdown & awaitterminate。

自动关闭功能有助于Project Loom将“结构化并发”引入Java。

try (
    ExecutorService executorService = Executors.… ;
) {
    // Submit your `Runnable`/`Callable` tasks to the executor service.
    …
}
// At this point, flow-of-control blocks until all submitted tasks are done/canceled/failed.
// After this point, the executor service will have been automatically shutdown, wia `close` method called by try-with-resources syntax.

有关Project Loom的更多信息，请搜索由Ron Pressler和Project Loom团队的其他人所做的演讲和采访。关注更近期的，如Project Loom的发展。

Project Loom技术的实验版本现在已经可以使用了，它是基于早期的Java 18。