java - 如果线程列表中的任何线程发生异常，则中断所有线程

Question

我正在使用 invokeAll() 调用线程列表。 AFAIK invokeAll() 将仅在所有线程完成其任务时返回。

ExecutorService threadExecutor = Executors.newFixedThreadPool(getThreadSize());
List<Future<Object>> future = w_threadExecutor.invokeAll(threadList);

当所有线程结束时调用

for (Future<Object> w_inProgressThread : w_future)
{
//

它停止发生异常的线程，而不是其余线程。如果任何线程抛出异常，有没有办法停止所有其他线程？还是我必须提交每个任务而不是 invokeAll()？？

我尝试在 invokeAll() 上使用 invokeAny() 而不是 invokeAll() 但没有取消剩余的任务invokeAny() :如果其中一个任务完成(或抛出异常)，则 Callable 的其余部分将被取消。引用:http://tutorials.jenkov.com/java-util-concurrent/executorservice.html

更新:

CompletionService<Object> completionService = new ExecutorCompletionService<Object>(w_threadExecutor);
                List<Future<Object>> futures = new ArrayList<Future<Object>>();
                for(Thread w_mt : threadList)
                {
                 futures.add(completionService.submit(w_mt));
                }
                for (int numTaken = 0; numTaken < futures.size(); numTaken++) {
                    Future f = completionService.take();
                    try {
                      Object result = f.get();
                      System.out.println(result);  // do something with the normal result
                    } catch (Exception e) {
                      System.out.println("Catched ExecutionException, shutdown now!");
                      //threadExecutor.shutdownNow();
                      Thread.currentThread().interrupt();

                      for (Future<Object> inProgressThread : futures)
                         {
                             inProgressThread.cancel(true);
                         } 
                      break;
                    }

更新 1:

按照waltersu的建议我试过了

ExecutorService threadExecutor = Executors.newFixedThreadPool(3);
              CompletionService<Object> completionService = new ExecutorCompletionService<Object>(threadExecutor);
              List<Future<Object>> futures = new ArrayList<Future<Object>>();
              futures.add(completionService.submit(new Callable<Object>() {
                @Override
                public Object call() throws Exception {
                    String s=null;
                //  Thread.sleep(1000);
                  for(int i=0; i < 1000000; i++){
                        int j =10 ;
                        if(i==100)
                        {

                        s.toString();
                        }

                        System.out.println("dazfczdsa :: " + i);
                    }
                  //throw new Exception("This is an expected Exception");
                return s;
                }
              }));
              futures.add(completionService.submit(new Callable<Object>() {
                @Override
                public Object call() throws Exception {
                    for(int i=0; i < 1000000; i++){
                        int j =0 ;
                        j= j+2;
                        System.out.println("dasa :: " + i);
                    }
                  Thread.sleep(3000);

                  return "My First Result";
                }
              }));

              while (futures.size() > 0) {
                Future f = completionService.take();
                futures.remove(f);
                try {
                  Object result = f.get();
                  System.out.println(result);  // do something with the normal result
                } catch (ExecutionException e) {
                  System.out.println("Caught exception from one task: " + e.getCause().getMessage() + ". shutdown now!");
                  f.cancel(true);
                  threadExecutor.shutdownNow();
                  break;
                }
              }
              System.out.println("Main exists");

异常发生时不会停止

Answer 1

你必须一个一个地submit()，而不是invokeAll()，然后检查Future是否有Exception。

public static void main(String[] args) throws InterruptedException {
  ExecutorService threadExecutor = Executors.newFixedThreadPool(3);
  CompletionService<Object> completionService = new ExecutorCompletionService<>(threadExecutor);
  List<Future<Object>> futures = new ArrayList<>();
  futures.add(completionService.submit(new Callable<Object>() {
    @Override
    public Object call() throws Exception {
      Thread.sleep(1000);
      throw new Exception("This is an expected Exception");
    }
  }));
  futures.add(completionService.submit(new Callable<Object>() {
    @Override
    public Object call() throws Exception {
      Thread.sleep(3000);
      return "My First Result";
    }
  }));

  while (futures.size() > 0) {
    Future f = completionService.take();
    futures.remove(f);
    try {
      Object result = f.get();
      System.out.println(result);  // do something with the normal result
    } catch (ExecutionException e) {
      System.out.println("Caught exception from one task: " + e.getCause().getMessage() + ". shutdown now!");
      threadExecutor.shutdownNow();
      break;
    }
  }
  System.out.println("Main exists");
}

---

更新 1:(回答 op 的更新 1 问题)

那是因为你的任务有一个长循环，它不检查中断，这使得你的任务不可取消。那你怎么阻止它？我认为您必须修改其他任务以使其可取消。作为the official doc说:

What if a thread goes a long time without invoking a method that throws InterruptedException? Then it must periodically invoke Thread.interrupted, which returns true if an interrupt has been received. For example:

for (int i = 0; i < inputs.length; i++) {
    heavyCrunch(inputs[i]);
    if (Thread.interrupted()) {
        // We've been interrupted: no more crunching.
        return;
    }
}

如果你不想修改你的任务又想让它快速停止怎么办？有一种方法可以停止不可取消的线程。它是 Thread.stop()。但是，起初，如果不使用反射，就无法从线程池中获取线程。此外，根据 javadoc，它已被弃用，因为“它本质上是不安全的” .

因此，最好的做法(我认为)是检查任务(或部分代码)中的中断，这些中断既不可取消又需要很长时间才能完成。