QueueUsingLinkedList.java

// Write a Program to implement Queue operations using linked list. 

public class Lab_2_Queue { 
    private Node front, rear; 
    private int queueSize; 
    
    private class Node { 
        int data;
        Node next;
    }
    public Lab_2_Queue(){
        front = null;
        rear = null;
        queueSize = 0;
    }
    public boolean isEmpty(){
        return (queueSize == 0);
    }
    public int dequeue(){
        int data = front.data;
        front = front.next;
        if (isEmpty()){
            rear = null;
        }
        queueSize--;
        System.out.println("Element " + data+ " removed from the queue");
        return data;
    }
    public void enqueue(int data){
        Node oldRear = rear;
        rear = new Node();
        rear.data = data;
        rear.next = null;
        if (isEmpty()){
            front = rear;
        }
        else {
            oldRear.next = rear;
        }
        queueSize++;
        System.out.println("Element " + data+ " added to the queue");
    }
    
    public void print_frontRear() {
        System.out.println("Front of the queue:" + front.data + " Rear of the queue:" + rear.data);
    }
}
class Queue{
    public static void main(String a[]){
        Lab_2_Queue queue = new Lab_2_Queue();
        
        queue.enqueue(15);
        queue.enqueue(8);
        queue.print_frontRear();
        queue.enqueue(38);
        queue.enqueue(32);
        queue.dequeue();
        queue.dequeue();
        queue.enqueue(4);
 
        queue.print_frontRear();
    }
}