class Mysterator implements Iterator { private int nextValue; public Mysterator (int start) { nextValue = start; } } public boolean hasNext() { return nextValue < 64; } public Integer next() { int result = nextValue; nextValue *= 2; return result; } public static void main(String[] args) { Iterator it = new Mysterator (2); while (it.hasNext()) { System.out.println(it.next()); } 5. What is the useful invariant of the above iterator? Write it in the following form (two blanks).