How to do function composition?

Question

While rather impatiently waiting for Java 8 release and after reading brilliant \'State of the Lambda\' article from Brian Goetz I noticed that function composition was not

Answer 1

There is one flaw in using compose and andThen. You have to have explicit variables, so you can't use method references like this:

(Person::getAddress).andThen(Address::getCountry)

It won't be compiled. What a pity!

But you can define an utility function and use it happily:

public static <A, B, C> Function<A, C> compose(Function<A, B> f1, Function<B, C> f2) {
        return f1.andThen(f2);
    }

compose(Person::getAddress, Address::getCountry)

Answer 2

There is a default interface function Function::andThen and Function::compose:

Function<Person, String> toCountry = personToAddress.andThen(addressToCountry);