Lab 2 - Queue

public class Queue {

    long[] queueArray;
    int front;
    int rear;
    int maxSize;
    int nItems;

    // Constructors
    public Queue(){

        front = 0;
        rear = -1;
        maxSize = 0;
        nItems = 0;
        queueArray = new long[0];
    }

    public Queue(int maxSize) {

        front = 0;
        rear = -1;
        this.maxSize = maxSize;
        nItems = 0;
        queueArray = new long[maxSize];
    }

    // Methods
    public boolean isEmpty() {

        if(nItems == 0) {

            return true;
        }

        else {

            return false;
        }
    }

    public boolean isFull() {

        return (nItems == maxSize);
    }

    public int size() {

        return nItems;
    }

    public void printQueue() {

        for(int i=front; i<=rear; i++) {

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

        System.out.println();
        System.out.println();
    }

    public void insert(long j) {

        if(isFull()) {

            System.out.println("Queue is full! " + j + " cannot be inserted.");
        }

        else {

            //if(rear == maxSize - 1) {

                for(int i=0; i<nItems; i++) {

                    // Shift
                    queueArray[i] = queueArray[i + front];
                }

                front = 0;
                rear = nItems - 1;

            //}

            rear++;
            queueArray[rear] = j;
            nItems++;
        }
    }

    public long remove() {

        if(isEmpty()) {

            System.out.println("Queue is empty. There are no items to be removed.");
            return -10000;
        }

        long temp = queueArray[front];
        front++;
        nItems--;

        if(front == maxSize) {

            front = 0;
            rear = -1;
        }

        return temp;
    }

    public long peek() {

        if(isEmpty()) {

            System.out.println("Queue is empty. Could not return the first element of the queue.");
            return -10000;
        }

        return queueArray[front];
    }

    public static void main(String[] args) {

        Queue queue = new Queue(5);

        // 1st insert
        System.out .println("After the insert of 10, 20, 30, 40 ,45, 50:");
        queue.insert(10);
        queue.insert(20);
        queue.insert(30);
        queue.insert(40);
        queue.insert(45);
        queue.insert(50);
        queue.printQueue();

        // 1st remove
        System.out.println("After removing the 3 first elements:");
        for(int i=0; i<3; i++) {

            queue.remove();
        }

        queue.printQueue();

        // 2nd insert
        System.out.println("After the insert of 55, 60, 70, 80:");
        queue.insert(55);
        queue.insert(60);
        queue.insert(70);
        queue.insert(80);
        queue.printQueue();

        // 2nd remove
        System.out.println("After removing all the 5 elenments of the queue:");
        for(int i=0; i<queue.size(); i++) {

            queue.remove();
        }



    }




}