private Stack(List<E> data, int bottomElement) {
this.data = data;
this.bottomElement = bottomElement;
}
public void push(E value) {
<BUG>data.add(value);
}</BUG>
private void checkNonEmpty() {
if (isEmpty()) throw new StackUnderflowException();
}

private Stack(List<E> data, int bottomElement) {
this.data = data;
this.bottomElement = bottomElement;
}
public void push(E value) {
data.add(value);
}
public void pushAll(Collection<E> values) {
data.addAll(values);
}
private void checkNonEmpty() {
if (isEmpty()) throw new StackUnderflowException();
}
