В образцовом решении интерфейс Apartment не используется вовсе. Зачем он тогда нужен ? Вариант через forEach c измененной функцией cleanRoom не принимается
package com.javarush.task.task14.task1415;
import java.util.ArrayList;
import java.util.List;
/*
Клининговый центр
*/
public class Solution {
public static void main(String[] args) {
List<Apartment> apartments = new ArrayList<Apartment>();
apartments.add(new OneRoomApt());
apartments.add(new TwoRoomApt());
apartments.add(new ThreeRoomApt());
cleanAllApartments(apartments);
}
public static void cleanAllApartments(List<Apartment> apartments) {
apartments.forEach(Apartment::cleanRoom);
}
interface Apartment {
void cleanRoom();
}
static class OneRoomApt implements Apartment {
public void cleanRoom() {
System.out.println("1 room is cleaned");
}
}
static class TwoRoomApt implements Apartment {
public void cleanRoom() {
System.out.println("2 rooms are cleaned");
}
}
static class ThreeRoomApt implements Apartment {
public void cleanRoom() {
System.out.println("3 rooms are cleaned");
}
}
}