同步LinkedList中的java.util.NoSuchElementException

Question

Following synchronized Queue is accessed by number of producers and consumers, it is synchronized but it is still giving java.util.NoSuchElementException when extracting element from queue. What is the matter with it and how to resolve it.

public class Que{

    private Queue queue = new LinkedList();

    public synchronized void enqueue(Runnable r) {
      queue.add(r);
      notifyAll();
    }

    public synchronized Object dequeue(){
        Object object = null;
        try{
            while(queue.isEmpty()){
                  wait();
            }
        } catch (InterruptedException ie) {

        }
        object = (Object)queue.remove();// This line is generating exception
        return object;
    }

}

Answer 1

I found the problem and i have resolved it too. InterruptedException has occured and the interrupted status need to be restored in the catch statement and also need to be return as follows.

public class Que{

    private Queue queue = new LinkedList();

    public synchronized void enqueue(Runnable e) {
      queue.add(e);
      notifyAll();
    }

    public synchronized Object dequeue(){
        Object object = null;
        try{
            while(queue.isEmpty()){
                  wait();
            }
        } catch (InterruptedException ie) {
          Thread.currentThread().interrupt();//restore the status
           return ie;//return InterruptedException object 
        }
        object = (Object)queue.remove();// This line is generating exception
        return object;
    }

}