How to use Java Optional to elegantly replace Ternary operators

Question

A super simple question:

Here's my plain Java code using traditional ternary operator ?

public DateTime getCreatedAt() {
    return !recordA.isPresent() ? recordB.get().getCreatedAt() : recordA.get().getCreatedAt();
}

My best bet is following:

public DateTime getCreatedAt() {
    return recordA.map(
        record -> record.getCreatedAt())
        .orElse(recordB.get().getCreatedAt());
  }

This could compile, but looks like it's not behaving correctly. It always executes both branches, for e.g. when recordA isPresent(), it still executes recordB.get().getCreatedAt() which throws me

java.util.NoSuchElementException: No value present

Any help is appreciated!

Basically, I'd like to replace the traditional ternary operator with more advanced Optional/lamda features.

Answer 1

To avoid eagerly evaluating else-branches, use orElseGet, which takes an instance of the functional interface Supplier:

return recordA.map(
    record -> record.getCreatedAt())
    .orElseGet(() -> recordB.get().getCreatedAt());

Answer 2

My question about recordB being Optional got unanswered but if it is Optional then you cannot just safely call its get method, you need to check if it is empty or not. Here safe call to get record or null if both recordA and recordB are empty Otionals.

        recordA
            .map(Record::getCreatedAt)
            .orElseGet( () -> recordB.map(Record::getCreatedAt).orElse(null) );