functional programming - Concise way of composing Java method references? -


given java 8 method functions:

class foo { bar getbar() {} } class bar { baz getbaz() {} }

a composition of 2 accessors looks like:

function<foo, bar> getbarfromfoo = foo::getbar; function<bar, baz> getbazfrombar = bar::getbaz; function<foo, baz> getbazfromfoo = getbarfromfoo.andthen(getbazfrombar);

is there more concise way? seems work

((function<foo, bar>) foo::getbar).andthen(bar::getbaz)

but it's rather ugly. outer parens make sense precedence reasons, why cast necessary?

(foo::getbar::getbaz nice, alas...)

let's define functional interface:

@functionalinterface interface myfunctionalinterface {     bar getbar(foo f); }

we can simplify method reference foo::getbar bit,

(foo foo) -> foo.getbar();

which means "take foo , return bar". description, lot of methods suitable (for instance, our interface getbar , funtion<foo, bar> apply):

myfunctionalinterface f1 = (foo foo) -> foo.getbar(); function<foo, bar> f2 = (foo foo) -> foo.getbar();

that answer question why cast necessary.

to answer question whether there more concise way affirmatively, have set context. context unambiguously gives function continue working with:

class functions {     public static <i, o> function<i, o> of(function<i, o> function) {         return function;     } }  functions.of(foo::getbar).andthen(bar::getbaz);

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