Core Java

Queue Java Example

In this article, we will see an example of Queue in Java!

1. Introduction

Queues are an essential data structure in computer science and are widely used in various applications. They follow the First-In-First-Out (FIFO) principle, where the item that has been in the queue the longest is the first one to be removed. In Java, the Queue interface and its implementations provide a powerful toolkit for working with queues efficiently. In this article, we will explore different aspects of queues in Java and demonstrate code examples for their implementation and usage.

2. Creating a Queue in Java

To create a queue in Java, we can use the Queue interface, which is implemented by various classes like LinkedList and PriorityQueue. Here’s an example of creating a queue using LinkedList:

Queue<String> queue = new LinkedList<>();

3. Adding Elements to a Queue

We can add elements to a queue using the add() or offer() methods. Both methods add the specified element to the end of the queue.


4. Removing Elements from a Queue

To remove elements from a queue, we can use the remove() or poll() methods. Both methods remove and return the head of the queue.

String head = queue.remove();
String headOrNull = queue.poll();

5. Retrieving the Head of a Queue

To retrieve the head of a queue without removing it, we can use the element() or peek() methods.

String head = queue.element();
String headOrNull = queue.peek();

6. Checking if a Queue is Empty

We can check if a queue is empty using the isEmpty() method. It returns true if the queue is empty; otherwise, it returns false.

boolean isEmpty = queue.isEmpty();

7. Iterating over a Queue

We can iterate over the elements of a queue using an enhanced for loop or an iterator.

for (String element : queue) {

Iterator<String> iterator = queue.iterator();
while (iterator.hasNext()) {
    String element =;

8. Queue Implementations in Java

Java provides multiple implementations of the Queue interface to suit different requirements. Some popular implementations include LinkedList, PriorityQueue, and ArrayDeque. Here’s an example of using a PriorityQueue:

Queue<Integer> priorityQueue = new PriorityQueue<>();

while (!priorityQueue.isEmpty()) {
    int element = priorityQueue.poll();

9. Example Output

After running all the code we can see how its method works.

Fig. 1: Queue Java Output.
Fig. 1: Queue Java Output.

10. Conclusion

Queues are fundamental data structures used to manage elements in a First-In-First-Out manner. In Java, the Queue interface and its implementations provide a powerful and flexible toolkit for working with queues efficiently. By understanding how to create, add, remove, and iterate over queues, you can leverage their capabilities to build robust and efficient applications.

Remember to import the required Java packages (java.util.Queue, java.util.LinkedList, java.util.PriorityQueue, etc.) before using queues in your Java programs.

11. Download the Source Code

This was an example of Queue Java and how some basic methods are used!!

You can download the full source code of this example here: Queue Java Example

Odysseas Mourtzoukos

Mourtzoukos Odysseas is studying to become a software engineer, at Harokopio University of Athens. Along with his studies, he is getting involved with different projects on gaming development and web applications. He is looking forward to sharing his knowledge and experience with the world.
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