JuniorTheoryCommon

What does the program print?

JAVA

import java.util.function.Function;

public class Main {
    public static void main(String[] args) {
        Function<Integer, Integer> f = x -> x + 1;
        Function<Integer, Integer> g = x -> x * 2;
        System.out.println(f.andThen(g).apply(3));
    }
}

Expecting 7: f.andThen(g) reads left to right, first f and then g on its result, so 3 becomes 4 and then 8.
Expecting 4 or 6: the two functions form a chain, g receives the value f returned, and apply gives back the result of g.

What does f.compose(g).apply(3) print for the same f and g?
Why is Function still a functional interface although it has an andThen method?

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JuniorTheoryCommon

What does the program print?

JAVA

import java.util.function.Function;

public class Main {
    public static void main(String[] args) {
        Function<Integer, Integer> f = x -> x + 1;
        Function<Integer, Integer> g = x -> x * 2;
        System.out.println(f.andThen(g).apply(3));
    }
}

Expecting 7: f.andThen(g) reads left to right, first f and then g on its result, so 3 becomes 4 and then 8.
Expecting 4 or 6: the two functions form a chain, g receives the value f returned, and apply gives back the result of g.

What does f.compose(g).apply(3) print for the same f and g?
Why is Function still a functional interface although it has an andThen method?

Back to questions Open topic in roadmap →Answer it yourself — Quiz