DataStructure/Queue.java at master · manumaini/DataStructure · GitHub

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public class Queue {


	int[] arr;
	int front , rear;
	int SIZE;

	Queue(int SIZE){

		this.SIZE = SIZE;
		arr= new int[SIZE];
		front = rear = -1;
	}


	//add element
	public void enqueue(int data) {

		if(isFull()) {
			System.out.print("queue is full");
			return;
		}else {

			if(front == -1) front = 0;
			rear = (rear +1) % SIZE;
			arr[rear] = data;

		}

	}

	public int dequeue() {

		int element;

		if(isEmpty()) {
			System.out.print("queue is empty");
			return -1;

		}else {

			element = arr[front];

			if(front == rear) {
				front = -1 ;
				rear = -1;
			}else {
				front = (front +1) % SIZE;
			}


			return element;
		}

	}

	public void printQueue() {

		for(int i = front ; i != rear ; i = (i+1) % SIZE ) {

			System.out.print(arr[i]+" ");

		}

	}


	public boolean isFull() {

		if(front == 0 && rear == SIZE-1) return true;
		if(front == rear + 1 ) return true;

		return false;
	}


	public boolean isEmpty() {

		if(front == -1) return true;

		return false;
	}


	public static void main(String args[]) {

		Queue q = new Queue(5);

		q.enqueue(1);
		q.enqueue(2);
		q.enqueue(3);

		q.dequeue();
		q.enqueue(5);
		q.enqueue(5);
		q.enqueue(5);

		q.printQueue();


	}

}