// Can you spot the "memory leak"?
public class Stack {
    private Object[] elements;
    private int size = 0;
    private static final int DEFAULT_INITIAL_CAPACITY = 16;
    public Stack() {
        elements = new Object[DEFAULT_INITIAL_CAPACITY];
    }
    public void push(Object e) {
        ensureCapacity(); elements[size++] = e;
    }
    public Object pop() {
        if (size == 0) throw new EmptyStackException();
        return elements[ - size];
    }
     /**
     * Ensure space for at least one more element, roughly
     * doubling the capacity each time the array needs to grow. */
     private void ensureCapacity() { if (elements.length == size)
     elements = Arrays.copyOf(elements, 2 * size + 1); }
}