きのジェネ

package com.doilux.generics;

import java.util.List;
import java.util.function.Function;
import java.util.stream.Collectors;


public class Odai {

    public static void printA(List<Int> l) {
        l.forEach(Int::print);
    }

    public static <T extends Printable> void printB(List<T> l) {
        l.forEach(Printable::print);
    }


    public static <T extends HasTwice<T>> List<T> twiceB(List<T> l) {
        return l.stream()
                .map(HasTwice::twice)
                .collect(Collectors.toList());
    }

    public static <T extends HasTwice<T> & Printable<T>> List<T> twiceAndPrint(List<T> l) {
        return l.stream()
                .map(HasTwice::twice)
                .peek(v -> v.print())
                .collect(Collectors.toList());
    }

    public static <T extends HasTwice<T> & Printable<T>, R extends HasTwice<T> & Printable<T>> List<R>
    applyAndPrint(List<T> l, Function<HasTwice<?>, R> g) {
        return l.stream()
                .map(g)
                .peek(v -> v.print())
                .collect(Collectors.toList());
    }

}