Java8 simplify expression using Optional

Question

I have an code block:

public Builder withMultiValueMap(MultiValueMap<String, String> multiValueMap) {
  ...
  withRespondentId(Long.valueOf(multiValueMap.getFirst("respondentId")));
  ...
  return this;
}

Sometimes map can return null if no value for respondentId key. I can process it in old way using something like

  String respondentId = multiValueMap.getFirst("respondentId");
  withRespondentId(respondentId == null? null: Long.valueOf(respondentId));

...but I want do it better!

Is it possible simplify using java8 Optional or other stuff?

I don't know about better... `Optional.ofNullable(respondentId).map(Long::valueOf).orElse(null))` — Marko Topolnik, Sep 28 '16 at 15:09
Super. This is exactly i need! Thank you. please add an answer to mark it solved. — Sergii, Sep 28 '16 at 15:11
The code will be cleaner refactor such that the `withRespondentId` method doesn't require a `null` (maybe initialize with the `null` scenario set). You could then write `Optional.ofNullable(respondentId).map(Long::valueOf).ifPresent(this::withRespondentId);` — flakes, Sep 28 '16 at 15:20

score 1 · Accepted Answer · answered Sep 28 '16 at 15:26

1

The syntax that has the same result as this expression:

respondentId == null? null: Long.valueOf(respondentId)

is

Optional.ofNullable(respondentId).map(Long::valueOf).orElse(‌null)

Since it's actually longer, it's not a complete win, although it might pass as more readable.

answered Sep 28 '16 at 15:26

Marko Topolnik

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Yeah, I'd very much prefer the first version. – Louis Wasserman Sep 28 '16 at 15:57
@LouisWasserman If you have a nullable reference, I usually think it's a mistake to box it into an Optional for the purpose of calling Optional methods, only to unbox it immediately. – Stuart Marks Sep 28 '16 at 18:23
@StuartMarks yes? We're in agreement here. – Louis Wasserman Sep 28 '16 at 18:24

score 1 · Answer 2 · answered Sep 28 '16 at 15:31

1

If MultiValueMap is your own class, you can migrate getFirst to

Optional<V> getFirst(K key);

multiValueMap.getFirst(key).map(Long::valueOf).getOrElse(null);

answered Sep 28 '16 at 15:31

Sergei Rybalkin

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org.springframework.util.MultiValueMap – Sergii Sep 28 '16 at 15:55

Java8 simplify expression using Optional

2 Answers2