Java 8: Where is TriFunction (and kin) in java.util.function? Or what is the alternative?

Question

I see java.util.function.BiFunction, so I can do this:

BiFunction f = (x, y) -> { return 0; };

What if

Answer 1

You could also create your own function taking the 3 parameters

@FunctionalInterface
public interface MiddleInterface{
    boolean isBetween(F from, T to, V middleValue);
}

MiddleInterface middleInterface = 
(x,y,z) -> x>=y && y<=z; // true