这只是我的个人意见。 为了克服CountDownLatch预先知道任务数量的要求，您可以使用简单的Semaphore来使用旧的方式。

ExecutorService taskExecutor = Executors.newFixedThreadPool(4);
int numberOfTasks=0;
Semaphore s=new Semaphore(0);
while(...) {
    taskExecutor.execute(new MyTask());
    numberOfTasks++;
}

try {
    s.aquire(numberOfTasks);
...

在任务中调用s.release()就像调用latch.countDown()一样;

ExecutorService WORKER_THREAD_POOL 
  = Executors.newFixedThreadPool(10);
CountDownLatch latch = new CountDownLatch(2);
for (int i = 0; i < 2; i++) {
    WORKER_THREAD_POOL.submit(() -> {
        try {
            // doSomething();
            latch.countDown();
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
        }
    });
}

// wait for the latch to be decremented by the two remaining threads
latch.await();

如果doSomething()抛出一些其他异常，latch.countDown()似乎不会执行，那么我该怎么办?

您可以使用自己的ExecutorCompletionService子类来包装taskExecutor，并使用自己的BlockingQueue实现在每个任务完成时获得通知，并在完成的任务数量达到预期目标时执行任何回调或其他操作。

我刚刚写了一个示例程序来解决你的问题。这里没有给出简洁的实现，所以我将添加一个。虽然您可以使用executor.shutdown()和executor. awaitterminate()，但这不是最佳实践，因为不同线程所花费的时间是不可预测的。

ExecutorService es = Executors.newCachedThreadPool();
    List<Callable<Integer>> tasks = new ArrayList<>();

    for (int j = 1; j <= 10; j++) {
        tasks.add(new Callable<Integer>() {

            @Override
            public Integer call() throws Exception {
                int sum = 0;
                System.out.println("Starting Thread "
                        + Thread.currentThread().getId());

                for (int i = 0; i < 1000000; i++) {
                    sum += i;
                }

                System.out.println("Stopping Thread "
                        + Thread.currentThread().getId());
                return sum;
            }

        });
    }

    try {
        List<Future<Integer>> futures = es.invokeAll(tasks);
        int flag = 0;

        for (Future<Integer> f : futures) {
            Integer res = f.get();
            System.out.println("Sum: " + res);
            if (!f.isDone()) 
                flag = 1;
        }

        if (flag == 0)
            System.out.println("SUCCESS");
        else
            System.out.println("FAILED");

    } catch (InterruptedException | ExecutionException e) {
        e.printStackTrace();
    }

如果你连续使用了更多的ExecutionServices线程，并且想要等待每个EXECUTIONSERVICE完成。最好的办法是像下面这样;

ExecutorService executer1 = Executors.newFixedThreadPool(THREAD_SIZE1);
for (<loop>) {
   executer1.execute(new Runnable() {
            @Override
            public void run() {
                ...
            }
        });
} 
executer1.shutdown();

try{
   executer1.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS);

   ExecutorService executer2 = Executors.newFixedThreadPool(THREAD_SIZE2);
   for (true) {
      executer2.execute(new Runnable() {
            @Override
            public void run() {
                 ...
            }
        });
   } 
   executer2.shutdown();
} catch (Exception e){
 ...
}

我创建了以下工作示例。其思想是有一种方法来处理具有许多线程(由numberOfTasks/阈值通过编程确定)的任务池(我使用队列作为示例)，并等待所有线程完成后继续进行其他处理。

import java.util.PriorityQueue;
import java.util.Queue;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/** Testing CountDownLatch and ExecutorService to manage scenario where
 * multiple Threads work together to complete tasks from a single
 * resource provider, so the processing can be faster. */
public class ThreadCountDown {

private CountDownLatch threadsCountdown = null;
private static Queue<Integer> tasks = new PriorityQueue<>();

public static void main(String[] args) {
    // Create a queue with "Tasks"
    int numberOfTasks = 2000;
    while(numberOfTasks-- > 0) {
        tasks.add(numberOfTasks);
    }

    // Initiate Processing of Tasks
    ThreadCountDown main = new ThreadCountDown();
    main.process(tasks);
}

/* Receiving the Tasks to process, and creating multiple Threads
* to process in parallel. */
private void process(Queue<Integer> tasks) {
    int numberOfThreads = getNumberOfThreadsRequired(tasks.size());
    threadsCountdown = new CountDownLatch(numberOfThreads);
    ExecutorService threadExecutor = Executors.newFixedThreadPool(numberOfThreads);

    //Initialize each Thread
    while(numberOfThreads-- > 0) {
        System.out.println("Initializing Thread: "+numberOfThreads);
        threadExecutor.execute(new MyThread("Thread "+numberOfThreads));
    }

    try {
        //Shutdown the Executor, so it cannot receive more Threads.
        threadExecutor.shutdown();
        threadsCountdown.await();
        System.out.println("ALL THREADS COMPLETED!");
        //continue With Some Other Process Here
    } catch (InterruptedException ex) {
        ex.printStackTrace();
    }
}

/* Determine the number of Threads to create */
private int getNumberOfThreadsRequired(int size) {
    int threshold = 100;
    int threads = size / threshold;
    if( size > (threads*threshold) ){
        threads++;
    }
    return threads;
}

/* Task Provider. All Threads will get their task from here */
private synchronized static Integer getTask(){
    return tasks.poll();
}

/* The Threads will get Tasks and process them, while still available.
* When no more tasks available, the thread will complete and reduce the threadsCountdown */
private class MyThread implements Runnable {

    private String threadName;

    protected MyThread(String threadName) {
        super();
        this.threadName = threadName;
    }

    @Override
    public void run() {
        Integer task;
        try{
            //Check in the Task pool if anything pending to process
            while( (task = getTask()) != null ){
                processTask(task);
            }
        }catch (Exception ex){
            ex.printStackTrace();
        }finally {
            /*Reduce count when no more tasks to process. Eventually all
            Threads will end-up here, reducing the count to 0, allowing
            the flow to continue after threadsCountdown.await(); */
            threadsCountdown.countDown();
        }
    }

    private void processTask(Integer task){
        try{
            System.out.println(this.threadName+" is Working on Task: "+ task);
        }catch (Exception ex){
            ex.printStackTrace();
        }
    }
}
}

希望能有所帮助!