DSA: Circular Queue

package az.etibarli.queue;

public class CircularQueue<T> {

    private T[] queue;
    private int size = 0;
    private int front = 0;
    private int end = 0;

    public CircularQueue() {
        this(5);
    }

    public CircularQueue(int capacity) {
        queue = (T[]) new Object[capacity];
    }

    public boolean add(T element) {
        if (isFull()) {
            resize();
        }
        queue[end++] = element;
        end = end % queue.length;
        size++;
        return true;
    }

    public T remove() {
        if (isEmpty()) {
            return null;
        }
        T element = queue[front];
        queue[front] = null;
        front = (front + 1) % queue.length;
        size--;
        return element;
    }

    public T peek() {
        if (isEmpty()) {
            return null;
        }
        return queue[front];
    }

    public int size() {
        return size;
    }

    public boolean isEmpty() {
        return size == 0;
    }

    public boolean isFull() {
        return size == queue.length;
    }

    private void resize() {
        T[] newQueue = (T[]) new Object[queue.length * 2];
        for (int i = 0; i < size; i++) {
            newQueue[i] = queue[(front + i) % queue.length];
        }
        queue = newQueue;
        front = 0;
        end = size;
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder("[");
        for (int i = 0; i < size; i++) {
            int index = (front + i) % queue.length;
            sb.append(queue[index]);
            if (i != size - 1) {
                sb.append(", ");
            }
        }
        return sb.append("]").toString();
    }

}