java - 我怎么知道线程作业已经完成？

Question

在 B 类中，我如何知道线程的作业已完成？在属性之后，一些 worker 正在运行。在 B 类中，我需要知道 worker 是否完成？

public class A implements InitializingBean{
     public void method1(){
        ...
    }    
    @Override
    public void afterPropertiesSet() throws Exception {
        System.out.print("test after properties set");      
        // send threads to executorService
        ExecutorService executorService = Executors
                .newFixedThreadPool(4);
        for (int i = 0; i < 4; i++) {
            Worker worker = new Worker();       
            executorService.submit(worker);
        }
    }
}
public class Worker implements Callable<Void>{
    @Override       
    public void call(){
     ...
   }
}
public class B{
   public void methodB(){
      A a = new A();
     a.method1();
     ///Here How can i know the job of the workers are finished?
   }
}

Answer 1

使用监听器/回调模式让线程向监听器报告完成。这个简单的例子应该显示过程:

public interface ThreadCompleteListener {
    void workComplete();
}

public class NotifyingThread extends Thread {
    private Set<ThreadCompleteListener> listeners;
    // setter method(s) for adding/removing listeners to go here

    @Override
    public void run() {
        // do stuff
        notifyListeners();
    }

    private void notifyListeners() {
        for (ThreadCompleteListener listener : listeners) {
            listener.workComplete(); // notify the listening class
        }
    }
}

在你的听力课上:

NotifyingThread t = new NotifyingThread();
t.addListener(new ThreadCompleteListener() {
    void workComplete() {
        // do something
    }
});

t.start();