Functions.andThen

[orionll]

There are two methods in java.util.function.Function: compose and andThen. But Functions has only compose. Can we add andThen too?
It can be useful for chaining of method references (and more natural than compose):

Function<Employee, String> f = Functions.andThen(Employee::getName, String::toLowerCase);

[nick-someone]

Functions.compose is a (guava) static factory method to compose these functions, so the snippet you propose above can already be implemented as: Function<Employee, String> f = Functions.compose(Employee::getName, String::toLowerCase);

The two methods you mentioned are instance methods on java.util.Function (which guava's Function extends as of version 21.0), so it should be legal to do the following right now:

c.g.c.b.Function<Employee, String> getNameFn = Employee::getName;
java.util.function.Function<Employee, String> getLowerName = getNameFn.andThen(String::toLowerCase);

[nick-someone]

(I updated the previous comment as I didn't process that compose put the outer function first)

In any case, if you're in a position to use method references, you should be preferring java.util.function.Function. If you're stuck passing a j.u.f.Function to a place that requires a c.g.c.b.Function, you can use jufFunction::apply at the callsite, using the j.u.f.Function chaining methods to build your composed function.