TIL: Optional Monad in Java

Instead of this

public Optional<Integer> maybeAdd(Optional<Integer> a, Optional<Integer> b) {
    if (a.isPresent() && b.isPresent()) {
        return Optional.of(a.get() + b.get());
    } else {
        return Optional.empty();
    }
}

Compose like this

public Optional<Integer> maybeAddMindBlown(Optional<Integer> a, Optional<Integer> b) {
    return 
        a.flatmap(one ->
        b.flatmap(two ->
        Optional.of(one + two)
        ));
}