如何从可调用接口返回未来对象（ExecutorService.Submit的内部工作）

Question

我试图了解在运行ExecutorService.Submit（可调用）；时如何创建future对象

class FactorialCalculator implements Callable<Long> { 
  private int number; 
  public FactorialCalculator(int number) { 
    this.number = number; 
  } 
  @Override 
  public Long call() throws Exception { 
        return (number*number); 
  }
}

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 void submit(Callable command) {
        queue.put(command);
    }
}

MyThreadPool mypool = new MyThreadPool(10);
mypool.submit(new FactorialCalculator(10));

Answer 1

最简单的方法是将可调用的代码封装在一个未来请求中：

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

当然，更简单的解决方案是使用executors.newfixedthreadpool而不是自己重新实现它。