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https://issues.apache.org/jira/browse/GROOVY-10616?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Paul King closed GROOVY-10616.
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> Add peek extension method for Optional, OptionalInt, OptionalLong and
> OptionalDouble
> ------------------------------------------------------------------------------------
>
> Key: GROOVY-10616
> URL: https://issues.apache.org/jira/browse/GROOVY-10616
> Project: Groovy
> Issue Type: Improvement
> Components: groovy-jdk
> Reporter: Eric Milles
> Assignee: Eric Milles
> Priority: Minor
> Fix For: 5.0.0-alpha-1
>
>
> {{{}java.util.Optional{}}}, et al. do not offer a direct method for consuming
> the value if present but returning the optional unchanged. A "peek" method
> similar to {{Stream#peek(Consumer<? super T>)}} would allow this without
> having to resort to using {{filter}} and always returning true or {{map}} and
> always returning the value or {{tap}} and {{isPresent}} in tandem or
> ".stream().peek(...).findFirst()".
> I considered "tap" but decided to leave existing {{tap}} semantics unchanged
> in case it is used with optionals.
> Proposed extension methods:
> {code:java}
> <T> Optional<T> peek(Optional<T> self, Consumer<? super T> action)
> OptionalInt peek(OptionalInt self, IntConsumer action)
> OptionalLong peek(OptionalLong self, LongConsumer action)
> OptionalDouble peek(OptionalDouble self, DoubleConsumer action)
> {code}
> Example usage:
> {code:groovy}
> def test(Optional<?> opt) {
> opt.peek { print it } // only prints if value present
> opt.peek(it -> print it)
> opt.peek(this::print)
> }
> {code}
> Alternatives/workarounds:
> {code:groovy}
> def test(Optional<?> opt) {
> opt.filter { print it; true }
> opt.map { print it; return it }
> opt.tap { ifPresent(this::print) }
> opt.stream().peek(this::print).findFirst()
> }
> {code}
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