remove Cats() method fails

Question about the task

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Hi there, I have tried to figure it out but I am not sure why my code is not working properly. The remove Cats() method does not work. Does anybody have an idea how to solve this? Thanks.

1. Inside the Solution class, create public static classes Cat and Dog.
2. Implement the createCats method, which should return a set with 4 cats.
3. Implement the createDogs method, which should return a set with 3 dogs.
4. Implement the join method, which should return a combined set of all the animals (all the cats and dogs).
5. Implement the removeCats method, which should remove from the set pets all cats in the set cats.
6. Implement the printPets method, which should display all the animals in the set pets.
Each animal should be on a new line.

Requirements:

The program should display text on the screen.
There should be public static classes Cat and Dog inside the Solution class.
The Solution class's createCats() method must return a Set containing 4 cats.
The Solution class's createDogs() method must return a Set containing 3 dogs.
The Solution class's join() method should return a combined set of all the animals (all the cats and dogs).
The removeCats() method should remove from the set pets all cats in the set cats.
The printPets() method should display all the animals in the set pets. Each animal should be on a new line.

package com.codegym.task.task08.task0820; import java.util.HashSet; import java.util.Iterator; import java.util.Set; /* Animal set */ 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>(); result.add(new Cat ()); result.add(new Cat ()); result.add(new Cat ()); result.add(new Cat ()); return result; } public static Set<Dog> createDogs() { HashSet<Dog> set2 = new HashSet<>(); set2.add(new Dog()); set2.add(new Dog()); set2.add(new Dog()); return set2; } public static Set<Object> join(Set<Cat> cats, Set<Dog> dogs) { HashSet pets = new HashSet(); pets.addAll(cats); pets.addAll(dogs); return pets; } public static void removeCats(Set<Object> pets, Set<Cat> cats) { for (Cat cat:cats) { pets.remove(cats); } } public static void printPets(Set<Object> pets) { Iterator <Object> itr = pets.iterator(); while (itr.hasNext()) { System.out.println(itr.next()); } } public static class Dog { } public static class Cat { } }

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Russell

Level 9 , Galmpton, Brixham , United Kingdom

20 December 2020, 15:07

I would not have figured out the method for this. enhanced for loops are causing me issues. But am i right in saying its soemthing like "For(Cat cat : cats) " means "for each Cat object in cats" and then combined with the program block { pets.remove(cat); } basically means "if the created Cat object cat is also in pets, then remove it from pets?" i guess it uses the passed-in cats list to create a new object named cat each time it reads an element. So it would be able to compare just one object with the pets list, instead of all of the passed in cats which is not possible. i don't think im making any sense at this point. ARGGGHH

Nithin

Level 35 , Hyderabad, India

4 July 2019, 10:17

solution

in line 54 you wrote "cats" instead of "cat".

ProgrammerNewbie

Level 14 , United States

4 July 2019, 17:46

You are right! Thanks! Sometimes such a small thing can break your code, but it is a good lesson to learn. Thank you very much.