CODE EXAMPLE FOR JAVA

Java Queue Linked List Implementation

class LinkedListQueue
{
 private Node front, rear; 
 private int queueSize; // queue size 
  
 //linked list node
 private class Node { 
 int data;
 Node next;
 }
  
 //default constructor - initially front & rear are null; size=0; queue is empty
 public LinkedListQueue()
 {
 front = null;
 rear = null;
 queueSize = 0;
 }
 
 
//check if the queue is empty
 public boolean isEmpty()
 {
 return (queueSize == 0);
 }
  
 //Remove item from the front of the queue.
 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;
 }
  
 //Add data at the rear of the queue.
 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");
 }
 //print front and rear of the queue
 public void print_frontRear() {
     System.out.println("Front of the queue:" + front.data 
     + " Rear of the queue:" + rear.data);
 }
}
class Main{
 public static void main(String a[]){
  
 LinkedListQueue queue = new LinkedListQueue();
 
 queue.enqueue(6);
 queue.enqueue(3);
 queue.print_frontRear();
 queue.enqueue(12);
 queue.enqueue(24);
 queue.dequeue();
 queue.dequeue();
 queue.enqueue(9);
 
 queue.print_frontRear();
 }
}