Circular Queue

Circular Queue is also a linear data structure, which follows the principle of FIFO(First In First Out), but instead of ending the queue at the last position, it again starts from the first position after the last, hence making the queue behave like a circular data structure.Circular queue avoids the wastage of space in a regular queue.

Implementation using Java:

public class Queue {
	private int data[];
	private int front;
	private int rear;
	private int size;
	public Queue()
	{
		data= new int[5];
		front=-1;
		rear=-1;
	}
	public int size()
	{
		return size;
	}
	public boolean isEmpty()
	{
		if(size==0)
			return true;
		else
			return false;
	}
	public int front() throws QueueEmptyException
	{
		if(size==0)
		{
			throw new QueueEmptyException();
		}
		return data[front];
	}
	public void enqueue(int element) throws QueueFullException
	{
		if(size==data.length)
		{
			throw new QueueFullException();
		}
		if(size==0)
		{
			front=0;
		}
		rear=(rear+1)%data.length;
		data[rear]=element;
		size++;
	}
	public int dequeue() throws QueueEmptyException
	{
		if(size==0)
		{
			throw new QueueEmptyException();
		}
		int temp=data[front];
		front=(front+1)%data.length;
		size--;
		if(size==0)
		{
			front=-1;
			rear=-1;
		}
		return temp;
	}
	public static void main(String args[])
	{
		Queue q=new Queue();
			try
			{
				q.enqueue(10);
				q.enqueue(20);
				q.enqueue(30);
				q.enqueue(40);
				q.enqueue(50);
			}catch(QueueFullException e)
			{
				System.out.println(e);
			}
			try
			{
				q.dequeue();
				q.dequeue();
			}catch(QueueEmptyException e)
			{
				System.out.println(e);
			}
			 try {
			q.enqueue(60);
			q.enqueue(70);
	        	}catch(QueueFullException e)
			{
				System.out.println(e);
			}
	        	System.out.println("Succesfully inserted");
	 } 
}	

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