How to return value of optional after mapping in java 8

Question

I need to get the String value which is the identifier, but this return void instead of string value. How can I return the string value?

    String previousReadyForHome = information.getPreviousContact().ifPresent(val->{
      Arrays.stream(val.basic.identifiers).filter(s -> s.type == readyForHomeType)
        .map(s -> s.identifier).findFirst().orElse(null);
    });

Dont do ifPresent. but .map or .flatMap on the given Optional. — Zabuzard
– Zabuzard, Commented Jan 19, 2021 at 12:04

Sweeper · Accepted Answer · 2021-01-19 12:04:23Z

4

You should not use ifPresent, as you have found out, it returns void. Rather, you should use flatMap, which gives you another Optional<String>, which you can then use orElse to unwrap it to null.

String previousReadyForHome = information.getPreviousContact().flatMap(val->
  Arrays.stream(val.basic.identifiers).filter(s -> s.type == readyForHomeType)
    .map(s -> s.identifier).findFirst()
).orElse(null);

answered Jan 19, 2021 at 12:04

Sweeper

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Comments

A.Casanova · Accepted Answer · 2024-02-16 11:30:27Z

0

Assuming your classes names:

Optional<String> previousReadyForHome = information.getPreviousContact()
    .map(Contact::getBasic)
    .map(BasicInfo::getIdentifiers)
    .flatMap(identifiers -> Arrays.stream(identifiers)
        .filter(identifier -> identifier.getType() == readyForHomeType)
        .map(Identifier::getIdentifier)
        .findFirst());

It is just a more readable approach.

answered Feb 16, 2024 at 11:30

A.Casanova

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