A LIFO Queue - like a Stack

The last of the queues is a LIFO queue. This queue behaves like a stack. It follows LIFO ordering.

public static void main(final String[] args) {

      final Deque<Integer> deQ = new ArrayDeque<Integer>();
      final Queue<Integer> asLifoQ = Collections.asLifoQueue(deQ);
      asLifoQ.offer(4);
      asLifoQ.offer(5);
      asLifoQ.offer(6);
      System.out.println("LifoQueue Contents : " + asLifoQ);
      // should behave like a stack
      System.out.println(asLifoQ.poll());
      System.out.println(asLifoQ.poll());
      System.out.println(asLifoQ.poll());
   }

There is no direct way to create the same. We need to use the asLifoQueue method of Collections class to create a LIFO queue. Further this method requires an instance of Deque to be available . It will not work with any queue. The output is :

LifoQueue Contents : [6, 5, 4]
6
5
4

Be sure to pass and empty Deque as the parameter. Any elements already present in the deque are not treated in the LIFO order.