Queue Implementation using an array in java

In Previous post, Queue Data Structure We talked and learned about Queue data structure.

In this post, we will learn about Queue Implementation using an array in java?

Below is the complete source code:

package com.kkjavatutorials.queue;
/**
 * Queue Implementation using circular array
 * @author KK JavaTutorials
 */
public class Queue {
	
	private int maxSize;
	private int front;
	private int rear;
	private int currentSize;
	
	private int queueArray[];

	public Queue(int maxSize) {
		super();
		this.maxSize = maxSize;
		this.front = 0;
		this.rear = -1;
		this.currentSize =0;
		this.queueArray = new int[maxSize];
	}
	
	/**
	 * Method to EnQueue or insert an Item in Queue(rear)
	 * @param data Item to be inserted in Queue
	 */
	public void enQueue(int data) {
		//Checking if queue is full before inserting new Item
		if(isQueueFull()) {
			throw new RuntimeException("Queue is Full!!");
		}
		
		//We have to wrap the queue in case maxSize has reached
		if(rear == maxSize-1) {
			rear =-1;
		}
		queueArray[++rear] = data;
		System.out.println(data+" is added in Queue");
		currentSize++;
	}

	/**
	 * Method to DeQueue or Remove an Item From Queue
	 * @return return DeQueued or Removed Item from queue(front)
	 */
	public int deQueue() {
		//Checking if queue is Empty before Removing new item
		if(isQueueEmpty()) {
			throw new RuntimeException("Queue is Empty!!");
		}
		
		int result = queueArray[front++];
		//We have to wrap the queue in case maxSize has reached
		if(front == maxSize) {
			front = 0;
		}
		
		currentSize--;
		return result;
	}
	private boolean isQueueEmpty() {
		return currentSize == 0;
	}

	private boolean isQueueFull() {
		return maxSize ==  currentSize;
	}
	
	public int size() {
		return currentSize;
	}
	
}

package com.kkjavatutorials.queue;

/**

* Queue Implementation using circular array

* @author KK JavaTutorials

public class Queue {

private int maxSize;

private int front;

private int rear;

private int currentSize;

private int queueArray[];

public Queue(int maxSize) {

super();

this.maxSize = maxSize;

this.front = 0;

this.rear = -1;

this.currentSize =0;

this.queueArray = new int[maxSize];

}

/**

* Method to EnQueue or insert an Item in Queue(rear)

* @param data Item to be inserted in Queue

public void enQueue(int data) {

//Checking if queue is full before inserting new Item

if(isQueueFull()) {

throw new RuntimeException("Queue is Full!!");

}

//We have to wrap the queue in case maxSize has reached

if(rear == maxSize-1) {

rear =-1;

}

queueArray[++rear] = data;

System.out.println(data+" is added in Queue");

currentSize++;

}

/**

* Method to DeQueue or Remove an Item From Queue

* @return return DeQueued or Removed Item from queue(front)

public int deQueue() {

//Checking if queue is Empty before Removing new item

if(isQueueEmpty()) {

throw new RuntimeException("Queue is Empty!!");

}

int result = queueArray[front++];

//We have to wrap the queue in case maxSize has reached

if(front == maxSize) {

front = 0;

}

currentSize--;

return result;

}

private boolean isQueueEmpty() {

return currentSize == 0;

}

private boolean isQueueFull() {

return maxSize == currentSize;

}

public int size() {

return currentSize;

}

Client program which uses our custom Queue:

package com.kkjavatutorials.client;

import com.kkjavatutorials.queue.Queue;
/**
 * Client program which uses our custom Queue
 * @author KK JavaTutorials
 *
 */
public class ClientTest {

	public static void main(String[] args) {
		
		Queue queue =  new Queue(5);
		queue.enQueue(10);
		queue.enQueue(20);
		queue.enQueue(30);
		queue.enQueue(40);
		queue.enQueue(50);
		
		queue.deQueue();
		
		queue.enQueue(60);
		
		System.out.println(queue.size());
		
	}
}

package com.kkjavatutorials.client;

import com.kkjavatutorials.queue.Queue;

/**

* Client program which uses our custom Queue

* @author KK JavaTutorials

public class ClientTest {

public static void main(String[] args) {

Queue queue = new Queue(5);

queue.enQueue(10);

queue.enQueue(20);

queue.enQueue(30);

queue.enQueue(40);

queue.enQueue(50);

queue.deQueue();

queue.enQueue(60);

System.out.println(queue.size());

}

Output of the above program:

10 is added in Queue
20 is added in Queue
30 is added in Queue
40 is added in Queue
50 is added in Queue
60 is added in Queue
5

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