​

class Animal {

    String species;

    String habitat;

    Animal(String species, String habitat) {

        this.species = species;

        this.habitat = habitat;

    }

    public int hashCode() {

        return (species + habitat).hashCode();

    }

    public boolean equals(Object obj) {

        if (obj instanceof Animal) {

            Animal temp = (Animal)obj;

            return species.equals(temp.species) && habitat.equals(temp.habitat);

        } else {

            return false;

        }

    }

}

​

public class prog {

    public static void main(String[] args) {

        HashSet<Animal> hs = new HashSet<Animal>();

        hs.add(new Animal("고양이", "육지"));

        hs.add(new Animal("고양이", "육지"));

        hs.add(new Animal("고양이", "육지"));

        System.out.println(hs.size());

    }

}