Java ArrayDeque

In this tutorial, we will learn about the ArrayDeque, its contructors and methods and how to implement it in Java.

Java Collection frameworks provide ArrayDeque class and it implements Deque Interface.ArrayDeque in Java provides a way to apply resizable-array in addition to the implementation of the Deque interface. It is also known as Array Double Ended Queue or Array Deck. This is a special kind of array that grows and allows users to add or remove an element from both sides of the queue.

Constructors of the ArrayDeque

Methods of ArrayDeque

Apart from the methods inherited from its parent class/interface ,it has following methods :

Example

// Java code explaining the use of ArrayDeque class methods 

import java.util.*; 
public class CodeMistic 
{ 
	public static void main(String[] args) 
	{ 
		// Intializing an deque 
		Deque<Integer> d = new ArrayDeque<Integer>(10); 

		// add() method to insert 
		d.add(5); 
		d.add(8); 
		d.add(12); 
		d.add(9); 
		d.add(1); 
		for (Integer element : d) 
		{ 
			System.out.println("Element : " + element); 
		} 

		System.out.println("Using clear() "); 
		//clear() method 
		d.clear(); 

		// addFirst() method to insert at start 
		d.addFirst(10); 
		d.addFirst(20); 

		// addLast() method to insert at end 
		d.addLast(24); 
		d.addLast(14); 

		System.out.println("Above elements are removed now \n"); 

		//size() of ArrayDeque 
		System.out.println("Size of deque : " + d.size() + "\n"); 
		for (Integer element : d) 
		{ 
			System.out.println("Element : " + element); 
		} 

		// conatins() method 
		System.out.println("\nIs 10 present in deque : " + d.contains(10)); 



		// Iterator() : 
		System.out.println("\nElements of deque using Iterator :"); 
		for(Iterator itr = d.iterator(); itr.hasNext();) 
		{ 
			System.out.println(itr.next()); 
		} 


		// descendingIterator() : to reverse the deque order 
		System.out.println("\nElements of deque in reverse order :"); 
		for(Iterator dItr = d.descendingIterator(); dItr.hasNext();) 
		{ 
			System.out.println(dItr.next()); 
		} 

		// element() method : to get Head element 
		System.out.println("\nHead Element using element(): " + d.element()); 

		// getFirst() method : to get Head element 
		System.out.println("Head Element using getFirst(): " + d.getFirst()); 

		// getLast() method : to get last element 
		System.out.println("Last Element using getLast(): " + d.getLast()); 


		// isEmpty() method : 
		System.out.println("\nChecks whether deque is empty : " + d.isEmpty()); 

		//toArray() method : 
		Object[] arr = d.toArray(); 
		System.out.println("\nArray Size : " + arr.length); 

		System.out.print("Array elements : "); 
		for(int i=0; i<arr.length ; i++) 
			System.out.print(" " + arr[i]); 
	} 
} 


Output:

Element : 5
Element : 8
Element : 12
Element : 9
Element : 1
Using clear() 
Above elements are removed now 

Size of deque : 4

Element : 20
Element : 10
Element : 24
Element : 14

Is 10 present in deque : true

Elements of deque using Iterator :
20
10
24
14

Elements of deque in reverse order :
14
24
10
20

Head Element using element(): 20
Head Element using getFirst(): 20
Last Element using getLast(): 14

Checks whether deque is empty : false

Array Size : 4
Array elements :  20 10 24 14