Implementation

Java Implementation of Queue

Java provides a built-in interface for queues in the java.util package. The most common implementation of a queue is the LinkedList class, which implements the Queue interface.

Here's a basic example of using a queue in Java:

Using LinkedList to Implement a Queue

import java.util.LinkedList;
import java.util.Queue;

public class QueueExample {
    public static void main(String[] args) {
        // Create a Queue using LinkedList
        Queue<Integer> queue = new LinkedList<>();

        // Add elements to the queue (Enqueue operation)
        queue.add(10);
        queue.add(20);
        queue.add(30);
        queue.add(40);

        // Display the elements in the queue
        System.out.println("Queue: " + queue);

        // Remove an element from the queue (Dequeue operation)
        int removedElement = queue.remove();
        System.out.println("Removed Element: " + removedElement);

        // Display the elements in the queue after dequeue
        System.out.println("Queue after Dequeue: " + queue);

        // Peek at the front element of the queue without removing it
        int frontElement = queue.peek();
        System.out.println("Front Element: " + frontElement);

        // Check if the queue is empty
        boolean isEmpty = queue.isEmpty();
        System.out.println("Is the Queue empty? " + isEmpty);
    }
}

Explanation:

Import the Queue Interface and LinkedList Class:

import java.util.LinkedList;
import java.util.Queue;

Create a Queue:

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

Here, we create a queue of integers using the LinkedList class, which implements the Queue interface.

Add Elements to the Queue (Enqueue Operation):

queue.add(10);
queue.add(20);
queue.add(30);
queue.add(40);

We use the add() method to insert elements into the queue. Elements are added to the rear of the queue.

Display the Queue:

System.out.println("Queue: " + queue);

This prints the current elements in the queue.

Remove an Element from the Queue (Dequeue Operation):

int removedElement = queue.remove();
System.out.println("Removed Element: " + removedElement);

The remove() method removes and returns the front element of the queue.

Display the Queue after Dequeue:

System.out.println("Queue after Dequeue: " + queue);

This prints the queue after removing an element.

Peek at the Front Element:

int frontElement = queue.peek();
System.out.println("Front Element: " + frontElement);

The peek() method returns the front element without removing it from the queue.

Check if the Queue is Empty:

boolean isEmpty = queue.isEmpty();
System.out.println("Is the Queue empty? " + isEmpty);

The isEmpty() method checks if the queue is empty and returns a boolean value.

Conclusion

This example demonstrates the basic operations of a queue, including adding elements (enqueue), removing elements (dequeue), peeking at the front element, and checking if the queue is empty. The LinkedList class in Java provides an easy way to implement queues and leverage the powerful features of the Java Collections Framework.