Implementation Of Queue Using an Array

ArrayQueue.java

public class ArrayQueue<X> {
    private X[] data;
    private int front;
    private int end;
    
    public ArrayQueue() {
        front = -1;
        end = -1;
        data = (X[])new Object[1000];
    }

    public int size() {
        //if the queue is empty, we return 0
        if(front == -1 && end == -1) {
            return 0;
        }
        
        else {
            return end - front + 1;
        }
    }

    public void enQueue(X item) {
        //if the queue is full
        if((end + 1) % data.length == front) {
            throw new IllegalStateException("The Queue is full!");
        }
        //otherwise check to see if any items have been added to the queue yet
        else if(size() == 0) {
            front++;
            end++;
            data[end] = item;
        }
        //otherwise add the item to the end of the queue
        else {
            end++;
            data[end] = item;
        }
    }

    public X deQueue() {
        X item = null;

        //if the queue is empty we can't dequeue anything
        if(size() == 0) {
            throw new IllegalStateException("Can't dequeue because the queue is empty!");
        }
        //otherwise if this is the last item on the queue, the queue needs to get reset to empty
        else if(front == end) {
            item = data[front];
            data[front] = null;
            front = -1;
            end = -1;
        }
        //otherwise grab the front of the queue, return it and adjust the front pointer
        else {
            item = data[front];
            data[front] = null;
            front++;
        }

        return item;
    }

    public boolean hasObject(X item) {
        boolean found = false;

        // if the queue is empty just immediately return false
        if(size() == 0) {
            return found;
        }

        for(int i = front; i < end; i++) {
            if(data[i].equals(item)) {
                found = true;
                break;
            }
        }

        return found;
    }

    public X getObjectAtIndex(int position) {
        if(size() == 0 || position > size()) {
            throw new IllegalArgumentException("No items in the queue or the position is greater than the queue size");
        }

        int Index = 0;
        for(int i = front; i < end; i++) {
            if(Index == position) {
                return data[i];
            }
            Index++;
        }

        //if we didn't find the item in the stack throw an exception
        throw new IllegalArgumentException("Could not get item at position: " + position);
    }


}