Type name choosing :: An Interface name for functions returning a value

Question

It's always hard to choose better variable/Type names. I am stuck choosing a name for an interface

I want to classify functions based on whether they return values or not. Here are some choices I made and why I rejected them.

ReturningFunction  : a function which doesn't return is hung. I don't want to confuse
OutputtingFunction : a function which outputs to stdout can return void so we can't call it with this name
VoidFunction       : a function which is void?

I tried googling but no luck. Please suggest some names :)

Answer 1

You may wish to reuse the interfaces provided by Java or, if they're not sufficient, follow their naming convention in the java.util.function package:

Similar to VoidFunction:

Consumer<T> Represents an operation that accepts a single input argument and returns no result.

BiConsumer<T,​U> Represents an operation that accepts two input arguments and returns no result.

Similar to ReturningFunction:

Function<T,​R> Represents a function that accepts one argument and produces a result.

BiFunction<T,​U,​R> Represents a function that accepts two arguments and produces a result.

Supplier<T> Represents a supplier of results.

For "outputs to stdout", you probably don't want an interface at all. Instead, you'd want a concrete class like the following:

final class SystemOutConsumer<A> implements Consumer<A> {

    private final BiConsumer<PrintStream, A> printStreamABiConsumer;

    public SystemOutConsumer(
            final BiConsumer<PrintStream, A> printStreamABiConsumer) {

        this.printStreamABiConsumer = printStreamABiConsumer;
    }

    public void accept(final A a) {

        printStreamABiConsumer.accept(System.out, a);
    }
}