public Integer apply(String string) {
      return string.length();
    }
  }

  private static final Ordering<Integer> DECREASING_INTEGER = Ordering.<Integer>natural().reverse();

  public void testOnResultOf_natural() {
    Comparator<String> comparator =
        Ordering.<Integer>natural().onResultOf(StringLengthFunction.STRING_LENGTH);
    assertTrue(comparator.compare("to", "be") == 0);

    public Integer apply(String string) {
      return string.length();
    }
  }

  private static final Ordering<Integer> DECREASING_INTEGER = Ordering.<Integer>natural().reverse();

  public void testOnResultOf_natural() {
    Comparator<String> comparator =
        Ordering.<Integer>natural().onResultOf(StringLengthFunction.STRING_LENGTH);
    assertTrue(comparator.compare("to", "be") == 0);