Deletion in a Queue in Java

import java.util.*;

class Queue
{
  int front, rear, size;
  int capacity;
  int array[];

  public Queue (int capacity)
  {
    this.capacity = capacity;
    front = this.size = 0;
    rear = capacity - 1;
    array = new int[this.capacity];
  }

  // Queue is full when size becomes
  // equal to the capacity
  boolean isFull (Queue queue)
  {
    return (queue.size == queue.capacity);
  }

  // Queue is empty when size is 0
  boolean isEmpty (Queue queue)
  {
    return (queue.size == 0);
  }

  // Method to add an item to the queue.
  // It changes rear and size
  void enqueue (int item)
  {
    if (isFull (this))
      return;
    this.rear = (this.rear + 1) % this.capacity;
    this.array[this.rear] = item;
    this.size = this.size + 1;
    System.out.println (item + " enqueued to queue");
  }

  // Method to remove an item from queue.
  // It changes front and size
  int dequeue ()
  {
    if (isEmpty (this))
      return Integer.MIN_VALUE;

    int item = this.array[this.front];
    this.front = (this.front + 1) % this.capacity;
    this.size = this.size - 1;
    return item;
  }
  
  public void disp() 
  /* function to display the elements of the queue */ {
	    
		System.out.print("The elements in the queue are:");
		if(front == -1) {
			System.out.print("\nQueue is Empty");
		} 
                else {
			for(int i = front; i <= rear; i++) {
				System.out.print(array[i] + "  ");
			}
		}
		System.out.println();
	}

}

// Driver class
public class Main
{
  public static void main (String[]args)
  {
    Queue queue = new Queue (1000);

      queue.enqueue (10);
      queue.enqueue (20);
      queue.enqueue (30);
      queue.enqueue (40);
      queue.disp();
      System.out.println ();
      
      System.out.println (queue.dequeue () + " dequeued from queue");
      System.out.println (queue.dequeue () + " dequeued from queue");
      queue.disp();

  }
}

10 enqueued to queue
20 enqueued to queue
30 enqueued to queue
40 enqueued to queue
The elements in the queue are:10  20  30  40  

10 dequeued from queue
20 dequeued from queue
The elements in the queue are:30  40