java – 如何覆盖executorService shutdown方法

我正在创建自己的线程池和将来可以执行可调用接口并行的对象. Executor提供shutdown方法来阻止所有工作线程运行.如果我正在创建一个类似下面的线程池,我应该如何在所有线程完成执行后实现shutdown方法停止?

我的自定义线程池看起来像this

class MyThreadPool implements java.util.concurrent.Executor 
{
    private final java.util.concurrent.BlockingQueue<Callable> queue;

    public MyThreadPool(int numThreads) {
        queue = new java.util.concurrent.LinkedBlockingQueue<>();
        for (int i=0 ; i<numThreads ; i++) {
            new Thread(new Runnable(){
                @Override
                public void run() {
                    while(true) {
                        queue.take().call();
                    }
                }
            }).start();
        }
    }

  @Override
  public <T> Future<T> submit(Callable<T> callable) {
    FutureTask<T> future = new FutureTask(callable);
    queue.put(future);
    return future;
  }

  public void shutdown(){ }
}

我想不出一种方法来保持线程列表,然后检查它们是否空闲?

解决方法:

你肯定应该持有你正在创建的线程的引用.例如,设置List< Thread>类型的字段线程.并从构造函数中将线程添加到此列表中.

之后,您可以在Thread#join()的帮助下实现shutdown():

public void shutdown() {
    for (Thread t : threads) {
        try {
            t.join();
        } catch (InterruptedException e) { /* NOP */ }
    }
}

不要忘记用适当的条件(在shutdown()中切换)替换while(true)并考虑使用BlockingQueue#poll(long, TimeUnit)而不是take().

编辑:像:

public class MyThreadPool implements Executor {

    private List<Thread> threads = new ArrayList<>();
    private BlockingDeque<Callable> tasks = new LinkedBlockingDeque<>();
    private volatile boolean running = true;

    public MyThreadPool(int numberOfThreads) {
        for (int i = 0; i < numberOfThreads; i++) {
            Thread t = new Thread(() -> {
                while (running) {
                    try {
                        Callable c = tasks.poll(5L, TimeUnit.SECONDS);
                        if (c != null) {
                            c.call();
                        }
                    } catch (Exception e) { /* NOP */ }
                }
            });
            t.start();
            threads.add(t);
        }
    }

    public void shutdown() {
        running = false;
        for (Thread t : threads) {
            try {
                t.join();
            } catch (InterruptedException e) { /* NOP */ }
        }
    }

    // ...

}
上一篇:基础线程机制--Executor线程池框架


下一篇:java-在动态线程号中调用ExecutorService.shutdown