Java Collections asLifoQueue() Method

The asLifoQueue() is an inbuilt method of Java Collections class which returns a view of a Deque as a Last-in-first-out (LIFO) Queue. In this method, the method add and remove is mapped to push and pop operation respectively. It is useful when we want to use a method requiring a Queue but we need LIFO order.

Syntax

Following is the declaration of asLifoQueue() method:

Parameter

Parameter	Description	Required/Optional
dequeue	Dequeue the provided collection List.	Required

Returns

The asLifoQueue() method returns queue list as a result of the method call.

Exceptions

Compatibility Version

Java 1.6 and above

Example 1

import java.util.*;
public class CollectionsAsLifoQueueExample1 {
	public static void main(String[] args) {
		Deque<String> dque = new ArrayDeque<String>(5);
            dque.add("Java");
            dque.add("C");
            dque.add("C++");
            dque.add("Unix");
            dque.add("Perl");        
            Queue<String> q = Collections.asLifoQueue(dque);   
            System.out.println("The resultant queue is: "+q);
	      }
}

Test it Now

Output:

The resultant queue is: [Java, C, C++, Unix, Perl]

Example 2

import java.util.*;
public class CollectionsAsLifoQueueExample2 {
	public static void main(String[] args) {
		Deque<Integer> deque = new ArrayDeque<Integer>(5);
		deque.add(1);
	      deque.add(2);
	      deque.add(3);
	      deque.add(4);
	      deque.add(5);          
            Queue<Integer> q = Collections.asLifoQueue(deque);   
            System.out.println("The resultant view of the queue is: "+q);
	      }
}

Test it Now

Output:

The resultant view of the queue is: [1, 2, 3, 4, 5]

Example 3

import java.util.*;
public class CollectionsAsLifoQueueExample3 {
	public static void main(String[] args) {
	   Deque<Integer> deque = new LinkedList<>();		
	   //Insert the specified element into the queue represented by this dequeue
         deque.offer(1);
         deque.offer(2);
         System.out.println("Initial view of the queue is: "+deque);
         deque.offer(3);
         System.out.println("New queue value is: "+deque);
         Queue<Integer> deque2 = Collections.asLifoQueue(deque);
         deque2.offer(4);
         deque2.offer(5); 
         System.out.println("The resultant view of the queue is: "+deque2);
	   }
}

Test it Now

Output:

Initial view of the queue is: [1, 2]
New queue value is: [1, 2, 3]
The resultant view of the queue is: [5, 4, 1, 2, 3]

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Java Collections asLifoQueue() Method

Syntax

Parameter

Returns

Exceptions

Compatibility Version

Example 1

Example 2

Example 3