Can run() return objects?

Question

Assuming that this is the scenario:

class A extends TimerTask{
  int a;
  public void run(){
    //operation to be performed periodically
  }
}

and

class B{
  int delay=2000,interval=3000;
  A objectA;
  public static void main(String[] args){
    Timer t=new Timer();
    t.scheduleAtFixedRate(new A(),delay,interval);
  }
}

Can't run() return objects? If I make such a change, incompatibility is cited. Why?

Answer 1

As you can see in the method-declaration, the returntype of run is void. Therefore the method can't directly return an object. But what you can do, is storing an object at the instance-level of class A and declaring a method on A from which you can get the stored object, when it's operation is finished

Answer 2

Use a FutureTask (and Future) with ExecutorService (see examples on API pages).

---

Example:

public static void main(String[] args) throws Exception {

     FutureTask<String> future = 
             new FutureTask<String>(new Callable<String>() {
         public String call() {
             try {
                 Thread.sleep(1000);
             } catch (InterruptedException e) {
                 e.printStackTrace();
             }
             return "Hello World!";
         }
     });

     ExecutorService executor = Executors.newFixedThreadPool(10);
     executor.execute(future);

     System.out.println(future.get());
}