Question

我需要从方法返回两种不同类型的变量（Future，ExecutorService）。我该怎么走？这是一段代码.. 我有一个A类，我试图在＆＃39; B＆＃39;中调用run（）方法。类。＆＃39; startExecutorService＆＃39;是启动threadExecutor和的方法＆＃39; stopExecutorService＆＃39;是停止threadExecutor的方法

 public class A{
    public static void main(String[] args){

        A AObj= new A();

        Future<?> task = null;
        ExecutorService threadexec = null;

        task = AObj.startExecutorService(task, threadexec);

        AObj.stopExecutorService(task, threadexec);

    }

    public Future<?> startExecutorService(Future<?> control, ExecutorService threadExecutor){

        //'noOfThreads' determines the total no of threads to be created in threadpool
        int noOfThreads = 1;  

        // Creating an object for class 'B' which has the run() method
        B ThreadTaskOne   = new ExecutorServiceThreadClass();

        // Calling the ExecutorService to create Threadpool with specified number of threads
        threadExecutor = Executors.newFixedThreadPool(noOfThreads);

        // Creating a Future object 'control' and thereby starting the thread 'ThreadTaskOne' 
         control = threadExecutor.submit(ThreadTaskOne);    

         return control;
    }

    public void stopExecutorService(Future<?> task, ExecutorService threadExecutor){

        // Interrupting the thread created by threadExecutor
        task.cancel(true);

        if(task.isCancelled()){
            System.out.println("Task has been cancelled !!");
        }

        // Closing the threadExecutor
        threadExecutor.shutdownNow();

    }

}

我得到了＆＃39; NullPointerException异常＆＃39; at＆＃39; stopExecutorService＆＃39; line in line＆＃39; threadExecutor.shutdownNow（）;＆＃39;出现此错误的原因是， threadExecutor值在main方法中没有改变。它仅在＆＃39; startExecutorService＆＃39;中发生了变化。方法。所以我想返回更改后的值 threadExecutor返回main方法，以及Future ..

请帮助我

Answer 1

创建一个复合类并返回该类的对象？

class A{
}

class B{
}

class Composite{
  A varA;
  B varB;
  public Composite(A ax, B by){ varA = ax; varB = by;}
  public A returnA(){ return varA;}
  public B returnB(){ return varB;}
}

class Executor{
    A a;
    B b;
 ////// code here 
    public Composite returnComposite{
     Composite c = new Composite(a,b);
     return c;
  }
}

如何从方法中返回两种不同类型的值？

1 个答案: