Question

I would like to emulate the following interface:

interface MultiSideEffectFunction<T> {
    void action(T first, T second);
}

(it would save me from having to introduce a new interface)

is there a preferred Guava approach to doing this?

Note: I thought about doing it with

Function<Pair<T>, Void>

but there are two problems which makes the creation of a new interface preferable:

1. One must define a class called Pair<T>, which looks a lot like a Map.Entry<T, T> with more appropriate getter names (as a second question: is there a Guava type like this?).
2. The Void return type is always a pain – it would be better to have a genuine void signature.

Answer 1

Guava contributor here.

The preferred Guava approach is to write your own interface.

In particular, do not use Function; Function should only be used when the function doesn’t have side effects.

Guava deliberately lacks a Pair type; we advise that any time you need a pair, you create your own class that attaches useful names to the two values, rather than the utterly uninformative “first” and “second”. (The prototypical example is for GPS coordinates; a class entitled LatLong is much more informative than a Pair<Double, Double>.)