public int compare(Stack<T> arg0, Stack<T> arg1) {
if (arg0.isEmpty()) {
return arg1.isEmpty() ? 0 : -1;
} else {
if (arg1.isEmpty()) return 1;
int rv = arg0.head().compareTo(arg1.head());
return rv == 0 ? compare(arg0.tail(), arg1.tail()) : rv;
}
}
public boolean hasNext() {
return !stack.isEmpty();
}
// Warning, uses equals to test for containment.
public boolean contains(Stack<T> stack) {
if (stack.isEmpty()) return true;
if (isEmpty()) return false; // stack is not empty
return head().equals(stack.head()) ? tail().contains(stack.tail()) : false;
}