Не могу понять почему не проходит код, нужна помощь
package com.javarush.task.task08.task0820;
import java.util.HashSet;
import java.util.Set;
/*
Множество всех животных
*/
public class Solution {
public static void main(String[] args) {
Set<Cat> cats = createCats();
Set<Dog> dogs = createDogs();
Set<Object> pets = join(cats, dogs);
printPets(pets);
removeCats(pets, cats);
printPets(pets);
}
public static Set<Cat> createCats() {
HashSet<Cat> result = new HashSet<Cat>();
for (int i = 0; i < 4; i++) {
Cat cat = new Cat();
result.add(cat);
}
return result;
}
public static Set<Dog> createDogs() {
HashSet<Dog> result = new HashSet<Dog>();
for (int i = 0; i < 3; i++) {
Dog dog = new Dog();
result.add(dog);
}
return result;
}
public static Set<Object> join(Set<Cat> cats, Set<Dog> dogs) {
HashSet<Object> all = new HashSet<Object>(cats);
all.addAll(dogs);
return all;
}
public static void removeCats(Set<Object> pets, Set<Cat> cats) {
HashSet<Object> catminus = new HashSet<Object>(pets);
catminus.removeAll(cats);
}
public static void printPets(Set<Object> pets) {
for (Object x : pets)
System.out.println(x);
}
public static class Cat {
}
public static class Dog {
}
}