How to implement Stack and Queue using ArrayDeque in Java
Last Updated : 24 Aug, 2022
ArrayDeque in Java
The 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. ArrayDeque class implements Queue and Deque interface which provides it a lot of methods and functionalities.
ArrayDeque Class in JAVAHow to use ArrayDeque
ArrayDeque is a class in Java Programming Language that implements the Queue and Deque interface that further extends the Collection Interface. ArrayDeque has all the methods of Queue and Deque such as add(), remove(), addFirst(), addLast(), removeFirst(), removeLast(), and many others inherited from these interfaces. It is very easy to use ArrayDeque class because of the ease of these methods provided in Java.
Insertion at the front
offerFirst() and addFirst() methods can be used to add element(s) at the front of the ArrayDeque. The main difference in between these two methods is that offerFirst() returns True if the element is added and returns False otherwise whereas addFirst() does not return a value.
Code implementation of the above methods:
Java import java.util.ArrayDeque; import java.util.Deque; public class GFG { // Driver Code public static void main(String[] args) { // Creating an ArrayDeque Deque<Integer> arrayDeque = new ArrayDeque<Integer>(); // Adding to front of ArrayDeque // using addFirst() method arrayDeque.addFirst(15); arrayDeque.addFirst(19); // Printing Arraydeque elements System.out.println( "Deque After Inserting using addFirst(): " + arrayDeque); // Adding to front of ArrayDeque // using offerFirst() method arrayDeque.offerFirst(17); arrayDeque.offerFirst(22); System.out.println( "Deque After Inserting using offerFirst(): " + arrayDeque); } } OutputDeque After Inserting using addFirst(): [19, 15] Deque After Inserting using offerFirst(): [22, 17, 19, 15]
Insertion at the back
offerLast() and addLast() methods can be used to add element(s) at the back of the ArrayDeque. The main difference in between these two methods is that offerLast() returns True if the element is added and returns False otherwise whereas addLast() does not return a value.
Code implementation of the above methods
Java import java.util.ArrayDeque; import java.util.Deque; public class GFG { // Driver Code public static void main(String[] args) { // Creating an ArrayDeque Deque<Integer> arrayDeque = new ArrayDeque<Integer>(); // Adding at the end of ArrayDeque // using addLast() method arrayDeque.addLast(15); arrayDeque.addLast(19); // Printing ArrayDeque elements System.out.println( "Deque After Inserting using addLast(): " + arrayDeque); // Adding at the end of ArrayDeque // using offerLast() method arrayDeque.offerLast(17); arrayDeque.offerLast(22); System.out.println( "Deque After Inserting using offerLast(): " + arrayDeque); } } OutputDeque After Inserting using addLast(): [15, 19] Deque After Inserting using offerLast(): [15, 19, 17, 22]
Deletion from the front
pollFirst() and removeFirst() can be used to remove the front element(s) from the ArrayDeque. The difference between these elements is that pollFirst() returns NULL if the ArrayDeque is empty whereas removeFirst() throws NoSuchElementException if the ArrayDeque is empty.
Code implementation for the above methods
Java import java.util.ArrayDeque; import java.util.Deque; public class GFG { // Driver Code public static void main(String[] args) { // Creating an ArrayDeque Deque<Integer> arrayDeque = new ArrayDeque<Integer>(); // Adding elements to the arrayDeque arrayDeque.add(15); arrayDeque.add(19); arrayDeque.add(17); arrayDeque.add(22); // Printing the elements of ArrayDeque System.out.println("Deque After Insertion: " + arrayDeque); // Removing element from the front // using removeFirst() method Integer i1 = arrayDeque.removeFirst(); System.out.println("Deleted Element: " + i1); // Printing the ArrayDeque System.out.println( "Deque after Deletion using removeFirst(): " + arrayDeque); // Removing element from the front // using pollFirst() method Integer i2 = arrayDeque.pollFirst(); System.out.println("Deleted Element: " + i2); System.out.println( "Deque after Deletion using pollFirst(): " + arrayDeque); } } OutputDeque After Insertion: [15, 19, 17, 22] Deleted Element: 15 Deque after Deletion using removeFirst(): [19, 17, 22] Deleted Element: 19 Deque after Deletion using pollFirst(): [17, 22]
Deletion from the end
pollLast() and removeLast() can be used to remove the back element(s) from the ArrayDeque. The difference between these elements is that pollLast() returns NULL if the ArrayDeque is empty whereas removeLast() throws NoSuchElementException if the ArrayDeque is empty.
Code implementation for the above methods
Java import java.util.ArrayDeque; import java.util.Deque; public class GFG { // Driver Code public static void main(String[] args) { // Creating an ArrayDeque Deque<Integer> arrayDeque = new ArrayDeque<Integer>(); // Adding elements to the arrayDeque arrayDeque.add(15); arrayDeque.add(19); arrayDeque.add(17); arrayDeque.add(22); // Printing the elements of ArrayDeque System.out.println("Deque After Insertion: " + arrayDeque); // Removing element from the end // using removeLast() method Integer i1 = arrayDeque.removeLast(); System.out.println("Deleted Element: " + i1); // Printing the ArrayDeque System.out.println( "Deque after Deletion using removeLast(): " + arrayDeque); // Removing element from the end // using pollLast() method Integer i2 = arrayDeque.pollLast(); System.out.println("Deleted Element: " + i2); System.out.println( "Deque after Deletion using pollLast(): " + arrayDeque); } } OutputDeque After Insertion: [15, 19, 17, 22] Deleted Element: 22 Deque after Deletion using removeLast(): [15, 19, 17] Deleted Element: 17 Deque after Deletion using pollLast(): [15, 19]
How to implement Stack using ArrayDeque
ArrayDeque can be easily used as a Stack as it provides the option to add and remove elements from both ends. There exists push() and pop() methods that make ArrayDeque favorable to be implemented as a Stack as it mimics the working of a usual Stack.
Code implementation of Stack using ArrayDeque
Java import java.util.ArrayDeque; import java.util.Deque; public class GFG { // Driver Code public static void main(String[] args) { // Creating an ArrayDeque to use // as a Stack Deque<Integer> stack = new ArrayDeque<Integer>(); // Inserting elements in the Stack // using push() operation stack.push(17); stack.push(19); stack.push(15); // Printing the elements System.out.println("Stack after insertion: " + stack); // Removing elements from the Stack // using pop() operation stack.pop(); System.out.println("Stack after deletion: " + stack); stack.pop(); System.out.println("Stack after deletion: " + stack); } } OutputStack after insertion: [15, 19, 17] Stack after deletion: [19, 17] Stack after deletion: [17]
How to implement Queue using ArrayDeque
ArrayDeque implements the Queue interface so it already has all the functionality provided by the interface. So, ArrayDeque can be used to perform all the normal queue operations using add() and remove() methods.
Code implementation of Queue using ArrayDeque
Java import java.util.ArrayDeque; import java.util.Deque; public class GFG { // Driver Code public static void main(String[] args) { // Creating a Queue using ArrayDeque Deque<Integer> queue = new ArrayDeque<Integer>(); // Adding the elements to the Queue queue.add(15); queue.add(17); queue.add(22); // Printing the elements of the Queue System.out.println("Queue after insertion: " + queue); // Removing elements from the queue queue.remove(); System.out.println("Queue after deletion: " + queue); queue.remove(); System.out.println("Queue after deletion: " + queue); } } OutputQueue after insertion: [15, 17, 22] Queue after deletion: [17, 22] Queue after deletion: [22]
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