resize()

/* Create a new internal array with a given capacity */
@SuppressWarnings("unchecked")
public void resize(int capacity) {
    Item[] copy = (Item[]) new Object[capacity];    // 1
    for (int i = 0; i < length; i++) {              // 2
        copy[i] = q[(i + head) % q.length];         // 2
    }                                               // 2
    head = 0;                                       // 3
    tail = length;                                  // 3
    q = copy;                                       // 4
}