Queue Using Linked List

QueueLinkedList.java

// A linked list (LL) node to store a queue entry
class QNode
{
    public int key;
    public QNode next;
     
    // constructor to create a new linked list node
    public QNode(int key) {
        this.key  = key;
        this.next = null;
    }
}
 
// A class to represent a queue
//The queue, front stores the front node of LL and rear stores ths
//last node of LL
class Queue
{
    QNode front, rear;
      
    public Queue() {
        front = rear = null;
    }
      
    // Method to add an key to the queue.  
    void enqueue(int n)
    {
        // Create a new LL node
        QNode temp = new QNode(n);
      
        // If queue is empty, then new node is front and rear both
        if (rear == null)
        {
           front = rear = temp;
           System.out.println("Queued: " + temp.key);
           return;
        }
      
        // Add the new node at the end of queue and change rear
        rear.next = temp;
        rear = temp;
        System.out.println("Queued: " + temp.key);
    }
      
    // Method to remove an key from queue.  
    QNode dequeue()
    {
        // If queue is empty, return NULL.
        if (front == null){
           System.out.println("Empty Queue");    
           return null;
        }
      
        // Store previous front and move front one node ahead
        QNode temp = front;
        System.out.println("Deqeued: " + temp.key);
        front = front.next;
      
        // If front becomes NULL, then change rear also as NULL
        if (front == null)
           rear = null;
        return temp;
    }
}
  
class Test
{
    public static void main(String[] args) 
    {
        Queue q = new Queue();
        q.enqueue(10);
        q.enqueue(20);
        q.dequeue();
        q.dequeue();
        q.enqueue(30);
        q.enqueue(40);
        q.enqueue(50);
        q.dequeue();
        q.dequeue();
        q.dequeue();
        q.dequeue();
        q.dequeue();
    }
}