Java ArrayDeque

🎓 Top 15 Udemy Courses (80-90% Discount): My Udemy Courses - Ramesh Fadatare — All my Udemy courses are real-time and project oriented courses.

▶️ Subscribe to My YouTube Channel (178K+ subscribers): Java Guides on YouTube

▶️ For AI, ChatGPT, Web, Tech, and Generative AI, subscribe to another channel: Ramesh Fadatare on YouTube

Introduction

The ArrayDeque class in Java, part of the java.util package, is a resizable array implementation of the Deque interface. It provides a double-ended queue, allowing elements to be added or removed from both ends.

Table of Contents

1. What is the ArrayDeque Class?
2. Features of ArrayDeque
3. Common Methods
4. Examples of Using ArrayDeque
5. Conclusion

1. What is the ArrayDeque Class?

ArrayDeque is a collection that supports element insertion and removal at both ends, offering an efficient alternative to linked lists and other deque implementations.

2. Features of ArrayDeque

• No capacity restrictions (dynamically resizable).
• Faster than LinkedList for queue operations.
• Not thread-safe (requires external synchronization for concurrent use).

3. Common Methods

• addFirst(E e): Inserts the specified element at the front.
• addLast(E e): Inserts the specified element at the end.
• offerFirst(E e): Inserts the specified element at the front without throwing an exception.
• offerLast(E e): Inserts the specified element at the end without throwing an exception.
• removeFirst(): Removes and returns the first element.
• removeLast(): Removes and returns the last element.
• pollFirst(): Retrieves and removes the first element, or returns null if empty.
• pollLast(): Retrieves and removes the last element, or returns null if empty.
• getFirst(): Retrieves, but does not remove, the first element.
• getLast(): Retrieves, but does not remove, the last element.
• peekFirst(): Retrieves, but does not remove, the first element, or returns null.
• peekLast(): Retrieves, but does not remove, the last element, or returns null.
• size(): Returns the number of elements in the deque.

4. Examples of Using ArrayDeque

Example 1: Basic Operations

This example demonstrates basic operations such as adding, removing, and accessing elements.

import java.util.ArrayDeque;

public class ArrayDequeExample {
    public static void main(String[] args) {
        ArrayDeque<String> deque = new ArrayDeque<>();

        // Adding elements
        deque.addFirst("First");
        deque.addLast("Last");
        System.out.println("Deque after additions: " + deque);

        // Accessing elements
        System.out.println("First element: " + deque.getFirst());
        System.out.println("Last element: " + deque.getLast());

        // Removing elements
        deque.removeFirst();
        deque.removeLast();
        System.out.println("Deque after removals: " + deque);
    }
}

Output:

Deque after additions: [First, Last]
First element: First
Last element: Last
Deque after removals: []

Example 2: Using offer and poll

This example shows the use of offer and poll methods for safe element insertion and removal.

import java.util.ArrayDeque;

public class OfferPollExample {
    public static void main(String[] args) {
        ArrayDeque<Integer> deque = new ArrayDeque<>();

        // Offering elements
        deque.offerFirst(1);
        deque.offerLast(2);
        System.out.println("Deque after offers: " + deque);

        // Polling elements
        System.out.println("Polled first: " + deque.pollFirst());
        System.out.println("Polled last: " + deque.pollLast());
        System.out.println("Deque after polls: " + deque);
    }
}

Output:

Deque after offers: [1, 2]
Polled first: 1
Polled last: 2
Deque after polls: []

Example 3: Peeking at Elements

This example demonstrates how to peek at elements without removing them.

import java.util.ArrayDeque;

public class PeekExample {
    public static void main(String[] args) {
        ArrayDeque<String> deque = new ArrayDeque<>();
        deque.add("Element");

        System.out.println("Peek first: " + deque.peekFirst());
        System.out.println("Peek last: " + deque.peekLast());
    }
}

Output:

Peek first: Element
Peek last: Element

5. Conclusion

The ArrayDeque class in Java is a versatile and efficient implementation of the Deque interface. It offers fast operations for both ends of the queue, making it a suitable choice for many applications that require double-ended queue functionality.

My Top and Bestseller Udemy Courses. The sale is going on with a 70 - 80% discount. The discount coupon has been added to each course below:

Build REST APIs with Spring Boot 4, Spring Security 7, and JWT

🆕 High-Demand 80–90% OFF

[NEW] Learn Apache Maven with IntelliJ IDEA and Java 25

🆕 High-Demand 80–90% OFF

ChatGPT + Generative AI + Prompt Engineering for Beginners

🚀 Trending Now 80–90% OFF

Spring 7 and Spring Boot 4 for Beginners (Includes 8 Projects)

🔥 Bestseller 80–90% OFF
Available in Udemy for Business

Building Real-Time REST APIs with Spring Boot - Blog App

🔥 Bestseller 80–90% OFF
Available in Udemy for Business

Building Microservices with Spring Boot and Spring Cloud

🌟 Top Rated 80–90% OFF
Available in Udemy for Business

Java Full-Stack Developer Course with Spring Boot and React JS

🔥 Bestseller 80–90% OFF
Available in Udemy for Business

Build 5 Spring Boot Projects with Java: Line-by-Line Coding

🌟 Top Rated 80–90% OFF

Testing Spring Boot Application with JUnit and Mockito

🔥 Bestseller 80–90% OFF
Available in Udemy for Business

Spring Boot Thymeleaf Real-Time Web Application - Blog App

🔥 Bestseller 80–90% OFF
Available in Udemy for Business

Master Spring Data JPA with Hibernate

🔥 Bestseller 80–90% OFF
Available in Udemy for Business

Spring Boot + Apache Kafka Course - The Practical Guide

🎓 Student Favorite 80–90% OFF
Available in Udemy for Business

Java Testing: Mastering JUnit 5 Framework

🆕 New 80–90% OFF

Reactive Programming in Java: Spring WebFlux and Testing

🌟 Top Rated 80–90% OFF

Spring Boot + RabbitMQ Course - The Practical Guide

🌟 Top Rated 80–90% OFF
Available in Udemy for Business

Functional Programming in Java (Includes Java Collections)

🎓 Student Favorite 80–90% OFF

ChatGPT for Java Developers: Boost Your Productivity with AI

🚀 Trending Now 80–90% OFF