如何检查在ExecutorService上运行的所有任务是否都已完成

I'v got ConcurrentLinkedDeque which I'm using for synchronic push/pop elements, and I'v got some async tasks which are taking one element from stack and if this element has neighbors It's pushing it to stack.

我有一个ConcurrentLinkedDeque，我用它来做同步推送/流行元素，我有一些异步任务，从堆栈中获取一个元素，如果这个元素有邻居，它就把它推到堆栈上。

Example code:

示例代码:

private ConcurrentLinkedDeque<Item> stack = new ConcurrentLinkedDeque<>();
private ExecutorService exec = Executors.newFixedThreadPool(5);

    while ((item = stack.pollFirst()) != null) {
                if (item == null) {
                } else {
                    Runnable worker = new Solider(this, item);
                    exec.execute(worker);
                }
            }

   class Solider{
         public void run(){
             if(item.hasNeighbors){
                for(Item item:item.neighbors){
                    stack.push(item)
                }
             } 
         }
    }

I would like to have additional statement in while loop which answers the question - "any task in Executor is working?"

我想在while循环中有更多的语句来回答这个问题——“Executor中的任何任务都在工作吗?”

1 个解决方案

#1

There isn't a clean way to check if all Runnables are done if you use ExecutorService.execute(Runnable). Unless you build a mechanism to do so in the Runnable itself (which is sloppy in my opinion).

如果您使用ExecutorService.execute(Runnable)，那么没有一种干净的方法来检查所有Runnables是否已经完成。除非您构建一种机制来在Runnable本身中实现这一点(在我看来这是草率的)。

Instead:
Use ExecutorService.submit(Runnable). This method will return a Future<?> which is a handle to the result of a runnable. Using Futures provides a clean way to check results.

相反:使用ExecutorService.submit(可运行)。此方法将返回一个Future 是一个可运行结果的句柄。使用期货提供了一种检验结果的干净方式。

All you have to do is maintain a list of Futures that you submit, and then you can iterate over the whole list of Futures and either:
A) wait for all the futures to be done in a blocking way or
B) check if all the futures are done in a non-blocking way.

所有你要做的就是保持一个期货,你提交的清单,然后就可以遍历整个列表的期货和:a)等所有的期货以阻塞方式做或B)检查是否所有的期货以非阻塞的方式进行。

Here is a code example:

下面是一个代码示例:

List<Future<?>> futures = new ArrayList<Future<?>>();
ExecutorService exec = Executors.newFixedThreadPool(5);

// Instead of using exec.execute() use exec.submit()
// because it returns a monitorable future
while((item = stack.pollFirst()) != null){
    Runnable worker = new Solider(this, item);
    Future<?> f = exec.submit(worker);
    futures.add(f);
}

// A) Await all runnables to be done (blocking)
for(Future<?> future : futures)
    future.get(); // get will block until the future is done

// B) Check if all runnables are done (non-blocking)
boolean allDone = true;
for(Future<?> future : futures){
    allDone &= future.isDone(); // check if future is done
}

#1