Queue Implementations in Java: A Comparative Analysis

Post author:Noel Kamphoa
Post published:June 26, 2025
Post category:Collections / Core Java Tutorials / Java Practitioner

1. Introduction

The Queue interface in Java, part of the Java Collections Framework, defines a data structure designed for holding elements prior to processing. In contrast to stacks, which operate on a LIFO (Last-In-First-Out) basis, queues typically operate on a FIFO (First-In-First-Out) principle.

“First come, first served—that’s the law of the queue.”

This article explores the main Queue implementations in Java, including their internal structures, performance characteristics, and appropriate use cases. For a broader perspective, refer to our article on Java Collections Overview.

2. Queue Implementations in Java

Java provides both general-purpose and concurrent queue implementations. Understanding the differences between these categories is crucial when selecting the right queue for a specific use case.

2.1 General-Purpose Queue Implementations

These queues are suitable for single-threaded or externally synchronized use cases.

LinkedList (as Queue)

LinkedList implements the Queue interface and behaves as a standard FIFO queue. It allows null elements and supports both ends via the Deque interface.

Use it when:

You need a simple FIFO queue.
You want flexibility with a double-ended queue.

Queue<String> queue = new LinkedList<>();
queue.offer("A");
queue.offer("B");
System.out.println(queue.poll()); // A

PriorityQueue

PriorityQueue orders elements based on their natural order or a custom comparator. It uses a min-heap structure internally.

Use it when:

Priority-based processing is required.
You want fast access to the highest-priority element.

Queue<Integer> pq = new PriorityQueue<>();
pq.offer(10);
pq.offer(1);
System.out.println(pq.poll()); // 1

ArrayDeque

ArrayDeque is a resizable array-based implementation of Deque. It offers efficient FIFO and LIFO operations.

Use it when:

You want a fast queue without thread safety.
You need double-ended access.

Queue<String> deque = new ArrayDeque<>();
deque.offer("X");
deque.offer("Y");
System.out.println(deque.poll()); // X

2.2 Concurrent Queue Implementations

These queues are designed for multithreaded environments and provide thread-safe access without external synchronization.

ConcurrentLinkedQueue

ConcurrentLinkedQueue is a lock-free, thread-safe implementation that performs well under high contention.

Use it when:

You need a fast, thread-safe FIFO queue.
You work in a non-blocking concurrent environment.

Queue<String> clq = new ConcurrentLinkedQueue<>();
clq.offer("Task1");
clq.offer("Task2");
System.out.println(clq.poll()); // Task1

PriorityBlockingQueue

PriorityBlockingQueue is a blocking queue with priority-based element ordering. It supports multiple producers and consumers.

Use it when:

You need a thread-safe priority queue.
Your application uses producer-consumer patterns.

BlockingQueue<Integer> pbq = new PriorityBlockingQueue<>();
pbq.put(100);
pbq.put(50);
System.out.println(pbq.take()); // 50

3. Performance Comparison

Implementation	Thread-Safe	FIFO	Priority Support	Nulls Allowed	Time Complexity (add/remove)
LinkedList	No	Yes	No	Yes	O(1)
PriorityQueue	No	No	Yes	No	O(log n)
ArrayDeque	No	Yes	No	No	O(1)
ConcurrentLinkedQueue	Yes	Yes	No	No	O(1)
PriorityBlockingQueue	Yes	No	Yes	No	O(log n)

“Each queue has a purpose—pick based on your access pattern and concurrency needs.”

4. When to Use Which

✅ Use LinkedList for general-purpose FIFO behavior with minimal constraints.
✅ Use ArrayDeque when you need fast, double-ended access and no thread safety.
✅ Use PriorityQueue or PriorityBlockingQueue when element ordering by priority is essential.
✅ Use ConcurrentLinkedQueue when working in concurrent, non-blocking environments.

5. Conclusion

Java offers a variety of queue implementations tailored to different performance and concurrency needs. Whether you need basic FIFO behavior, priority processing, or concurrent access, the Queue interface and its implementations provide flexible and efficient options.