public class Main {
  public static void main(String[] args) {
    Hero hero = new Hero("だいぱんまん", 100, 10);
    System.out.println(hero.toString()); // -> Hero@7852e922
  }
}

// toString()をオーバーライドしない場合
class Hero {
  private String name;
  private int hp;
  private int mp;

  Hero(String name, int hp, int mp) {
    this.name = name;
    this.hp = hp;
    this.mp = mp;
  }
}