'Find' method for Iterable

[Remi Forax]

----- Mail original -----
> De: "Nir Lisker" <nlisker at gmail.com>
> À: "core-libs-dev" <core-libs-dev at openjdk.java.net>
> Envoyé: Lundi 14 Septembre 2020 20:56:27
> Objet: 'Find' method for Iterable

> Hi,
> 
> This has probably been brought up at some point. When we need to find an
> item in a collection based on its properties, we can either do it in a
> loop, testing each item, or in a stream with filter and findFirst/Any.
> 
> I would think that a method in Iterable<T> be useful, along the lines of:
> 
> public <T> Optional<T> find(Predicate<T> condition) {
>    Objects.requireNonNull(condition);
>    for (T t : this) {
>         if (condition.test(t)) {
>             return Optional.of(t);
>        }
>    }
>    return Optional.empty();
> }
> 
> With usage:
> 
> list.find(person -> person.id == 123456);
> 
> There are a few issues with the method here such as t being null in
> null-friendly collections and the lack of bound generic types, but this
> example is just used to explain the intention.
> 
> It will be an alternative to
> 
> list.stream().filter(person -> person.id == 123456).findAny/First()
> (depending on if the collection is ordered or not)
> 
> which doesn't create a stream, similar to Iterable#forEach vs
> Stream#forEach.
> 
> Maybe with pattern matching this would become more appetizing.

During the development of Java 8, we first tried to use Iterator/Iterable instead of using a novel interface Stream.
But a Stream cleanly separate the lazy side effect free API from the mutable one (Collection) and can be optimized better by the VM (it's a push API instead of being a pull API).

The other question is why there is no method find() on Collection, i believe it's because while find() is ok for any DB API, find() is dangerous on a Collection because the execution time is linear, so people may use it instead of using a Map.

> 
> - Nir

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