[GROOVY-10616] Add peek extension method for Optional, OptionalInt, OptionalLong and OptionalDouble

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 5.0.0-alpha-1
• Component/s: groovy-jdk
• Assignee: Eric Milles
• Reporter: Eric Milles
• Created: 02/May/22 17:13
• Updated: 23/Aug/23 09:11
• Resolved: 24/Jun/22 12:55

Description

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:

<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)

Example usage:

def test(Optional<?> opt) {
  opt.peek { print it } // only prints if value present
  opt.peek(it -> print it)
  opt.peek(this::print)
}

Alternatives/workarounds:

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()
}

Issue Links

• is related to: GROOVY-10223 Add support for Optional to DefaultTypeTransformation.asCollection()