Guava Optional type, when transformation returns another Optional

Question

I have a method that procudes an Optional

But this String must be parsed at another application level as Integer or Long.

This I h

Answer 1

I guess you can do:

public static void main(final String[] args) {
  final Optional valid = Optional.of("42")
      .transform(STR_TO_INT_FUNCTION)
      .or(Optional.absent());
  System.out.println(valid); // Optional.of(42)
  final Optional invalid = Optional.of("Toto")
      .transform(STR_TO_INT_FUNCTION)
      .or(Optional.absent());
  System.out.println(invalid); // Optional.absent()
  final Optional absent = Optional.absent()
      .transform(STR_TO_INT_FUNCTION)
      .or(Optional.absent());
  System.out.println(absent); // Optional.absent()
}

private static final Function> STR_TO_INT_FUNCTION =
    new Function>() {
      @Override
      public Optional apply(final String input) {
        return Optional.fromNullable(Ints.tryParse(input));
      }
    };

Usage isn't that clumsy when you use Optional -> transform -> or in one line (assigning transformed optional integer would produce Optional>).