its101.md.wk.07.QueueImplementation

package its101.mdwk07;

class Queue {

    private static int front, rear, capacity;
    private static int[] queue;

    Queue(int size) {
        front = rear = 0;
        capacity = size;
        queue = new int[capacity];
    }

    // Create Enqueue() method, this will be use to insert an element into the queue
    static void enqueue(int item) {
        // Check if queue is full
        if (capacity == rear) {
            System.out.println("Error! Queue is overflow.");
        }
        // Insert element at the rear
        else {
            queue[rear] = item;
            rear++;
        }
    }

    // Create Dequeue() method, this will be use to remove an element from the queue
    static void dequeue() {
        // Check if queue is empty
        if (front == rear) {
            System.out.println("Error! Queue is underflow.");
        }
        // Shift elements to the right by one place until rear
        else {
            if (rear - 1 >= 0) System.arraycopy(queue, 1, queue, 0, rear - 1);
            // Set queue[rear] to 0
            if (rear < capacity)
                queue[rear] = 0;
            // Decrement rear
            rear--;
        }
    }

    // Create queuePrint() method, this will be use to print queue elements
    static void queuePrint() {
        int i;
        if (front == rear) {
            System.out.println("Queue is Empty");
            return;
        }
        // Traverse from front to rear and print elements
        for (i = front; i < rear; i++) {
            System.out.printf(" %d ", queue[i]);
        }
    }

    // Create queuePrint() method, this will be use to print the front of queue
    static void peek() {
        if (front == rear) {
            System.out.println("Queue is Empty");
            return;
        }
        System.out.printf("\nFront element of the queue: %d \n", queue[front]);
    }

    // Create isEmpty() method, this will check if the queue is empty
    public boolean isEmpty() {
        return (front == rear);
    }

    // Create isFull() method, this will check if the queue is full
    public boolean isFull() {
        return (rear == capacity);
    }
}

public class QueueFinal {
    public static void main(String[] args) {
        // Create a queue of capacity 5
        Queue ralph = new Queue(5);

        // Check if the queue is empty using isEmpty()
        boolean resultEmpty = ralph.isEmpty();
        System.out.println("Is queue empty: " + resultEmpty); // This will print true (queue is empty)

        // Insert elements in the queue using enqueue()
        ralph.enqueue(1);
        ralph.enqueue(2);
        ralph.enqueue(3);
        ralph.enqueue(4);
        ralph.enqueue(5);

        // Print Queue elements again using queuePrint()
        System.out.println("Element of the queue after enqueue operation: ");
        ralph.queuePrint(); // This will now print the new elements inserted to the queue

        // Check again if the queue is empty
        resultEmpty = ralph.isEmpty();
        System.out.println("\nIs queue empty: " + resultEmpty); // This will now print false (queue is not empty)

        // Dequeue elements using dequeue()
        ralph.dequeue();
        ralph.dequeue();

        // Print Queue elements after the dequeue operation
        System.out.println("Element of the queue after two dequeue operations: ");
        ralph.queuePrint();

        // Print the front of the queue using the peek()
        ralph.peek();

        // Check if the queue is full using isFull()
        boolean resultFull = ralph.isFull();
        System.out.println("Is queue full: " + resultFull);
    }
}