}

  // enum singleton pattern
  private enum TrimStringFunction implements Function<String, String> {
    INSTANCE;

    @Override
    public String apply(String string) {
      return whitespace().trimFrom(string);
    }
  }

  public void testCompose() {
    Function<String, String> trim = TrimStringFunction.INSTANCE;
    Predicate<String> equalsFoo = Predicates.equalTo("Foo");

  }

  // enum singleton pattern
  private enum TrimStringFunction implements Function<String, String> {
    INSTANCE;

    @Override
    public String apply(String string) {
      return whitespace().trimFrom(string);
    }
  }

  public void testCompose() {
    Function<String, String> trim = TrimStringFunction.INSTANCE;
    Predicate<String> equalsFoo = Predicates.equalTo("Foo");