Java8 method reference used as Function object to combine functions

Question

Is there a way in Java8 to use a method reference as a Function object to use its methods, something like:

Stream.of(\"ciao\", \"hola\", \"hello         


        

Answer 1

You should be able to achieve what you want inline by using casts:

Stream.of("ciao", "hola", "hello")
      .map(((Function) String::length).andThen(n -> n * 2))

There are only 'type hints' for the compiler, so they don't actually 'cast' the object and don't have the overhead of an actual cast.

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Alternatively, you can use a local variable for readability:

Function fun = String::length

Stream.of("ciao", "hola", "hello")
      .map(fun.andThen(n -> n * 2));

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A third way that may be more concise is with a utility method:

public static  Function chain(Function fun1, Function fun2)
{
    return fun1.andThen(fun2);
}

Stream.of("ciao", "hola", "hello")
      .map(chain(String::length, n -> n * 2));

Please note that this is not tested, thus I don't know if type inference works correctly in this case.