Java Deque Interface

Last Updated : 4 Apr 2026

Java Deque interface allows operations from both ends of a collection. In this chapter, you will learn about the Java Deque, its features, and how it supports insertion and deletion operations from both ends.

What is Java Deque?

A Deque (double-ended queue) is a linear collection that supports insertion and deletion of elements from both ends. The name deque is an abbreviation for double-ended queue.

There is no fixed limit on the number of elements a deque can contain. However, this interface supports both:

Capacity-restricted deques
Unbounded deques (no fixed size limit)

The Deque interface provides various methods to insert, remove, and examine elements.

These methods generally exist in two forms:

One that throws an exception when the operation fails
Another that returns a special value (null or false) depending on the operation.

Dequeue Methods

The java.util.Deque interface provides methods to perform double-ended queue operations in Java. Its commonly used implementation class is java.util.ArrayDeque.

The following table lists the important methods of the Deque interface along with their descriptions.

Methods	Description
add(E e)	This method is used to insert a specified element into the queue represented by the deque
addAll(Collection<? Extends E>c)	Adds all the elements in the specified collection at the end of the deque.
addFirst(E e)	Inserts the specified element at the front of the deque.
addLast(E e)	Inserts the specified element at the end of the deque.
contains(object o)	Returns true if the deque contains the specified element.
descendingIterator()	Returns an iterator over the elements in reverse sequential order.
element()	Retrieves the head of the queue represented by the deque.
getFirst()	Retrieves but does not remove the first element of the deque.
getLast()	Retrieves but does not remove the last element of the deque.
iterator()	Returns an iterator over the element in the deque in a proper sequence.
offer(E e)	Inserts the specified element into the deque, returning true upon success and false if no space is available.
offerFirst()	Inserts the specified element at the front of the deque unless it violates the capacity restriction.
offerLast()	Inserts the specified element at the end of the deque unless it violates the capacity restriction.
peek()	Retrieves but does not move the head of the queue represented by the deque or may return null if the deque is empty.
peekFirst()	Retrieves but does not move the first element of the deque or may return null if the deque is empty.
peekLast()	Retrieves but does not move the last element of the deque or may return null if the deque is empty.
poll()	Retrieves and remove the head of the queue represented by the deque or may return null if the deque is empty.
pollFirst()	Retrieves and remove the first element of the deque or may return null if the deque is empty.
pollLast()	Retrieves and remove the last element of the deque or may return null if the deque is empty.
pop()	Pops an element from the stack represented by the deque.
push()	Pushes an element onto the stack represented by the deque.
remove()	Retrieves and remove the head of the queue represented by the deque.
remove(Object o)	Removes the first occurrence of the specified element from the deque.
removeFirst()	Retrieves and remove the first element from the deque.
removeFirstOccurrence(Object o)	Remove the first occurrence of the element from the deque.
removeLast()	Retrieve and remove the last element from the deque.
removeLastOccurrence(Object o)	Remove the last occurrence of the element from the deque.
size()	Returns the total number of elements in the deque.

Examples of Java Deque

The following examples demonstrate how to use the Deque interface and its methods for performing operations like insertion, deletion, and traversal.

Example 1: Inserting, Popping, and Removing Elements

In this example, we create a Deque using ArrayDeque, insert elements, traverse them, and perform pop and remove operations.

import java.util.ArrayDeque;
import java.util.Deque;

public class JavaDequeExample1 {
  public static void main(String[] args) {
	Deque<Integer> deque = new ArrayDeque<Integer>();
	// Inserts the element.
	deque.add(1);
	deque.add(2);
	deque.add(3);
	System.out.println("Inserting three elements : ");
	for (Integer integer : deque) {
	System.out.println(integer);	
	}
	// Popping the element.
	deque.pop();
	System.out.println("After popping : ");
	for (Integer integer : deque) {
		System.out.println(integer);
	}
	deque.remove(3);
	System.out.println("Removing the element 3 :"+deque);
  }
}

Compile and Run

Output:

Inserting three elements : 
1
2
3
After popping : 
2
3
Removing the element 3 :[2]

Example 2: Adding Elements at Front and Removing Last Element

In this example, we add elements at the front of the deque, check its size, and remove the last element.

import java.util.ArrayDeque;
import java.util.Deque;

public class JavaDequeExample2 {
public static void main(String[] args) {
   Deque<String> deque = new ArrayDeque<String>();
   // Adding the element in the front of the deque.
   deque.addFirst("Java");
    System.out.println("The first element is : "+deque);
   // Again adding the element in the front of the deque.
    deque.addFirst("Python");
    System.out.println("After adding the next element in the front of the deque : "+deque);
     deque.add("Ruby");
     System.out.println("The final deque is  : "+deque);
   // Returns the number of elements.
     int size =  deque.size();
     System.out.println("The number of elements are : "+size);
    // Removes the last element.
     deque.removeLast();
 System.out.println("Deque after removing the last element is given as :  "+deque);
   }	
}

Compile and Run

Output:

The first element is : [Java]
After adding the next element in the front of the deque : [Python, Java]
The final deque is  : [Python, Java, Ruby]
The number of elements are : 3
Deque after removing the last element is given as :  [Python, Java]

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