Why is "instanceof" not working?

Question

I'm using the Java instanceof but it doesn't seem to be working.

I have three java classes that extend a Hero class.
The Hero.java class:

public abstract class Hero {

    protected int health;

    public Hero() { 
    }
}

The other three classes:

public class Archer extends Hero {
    public Archer() {
    }
}

public class Mage extends Hero {
    public Mage() {
    }
}

public class Warrior extends Hero {
    public Warrior() {
    }
}

I have this main class WelcomeScreen.java

public class WelcomeScreen {

    private Archer archer;
    private Mage mage;
    private Warrior warrior;
    private Hero hero;

public WelcomeScreen() {

        // choose a hero (archer/mage/warrior)
        hero = archer;
        new Game(hero);
    }

    public static void main(String args[]) {
        new WelcomeScreen();
    }

}

that instantiates the Game.java class

public class Game {

    public Game(Hero chosenHero) {

        if (chosenHero instanceof Mage) {
            System.out.println("you selected mage");
        } else if (chosenHero instanceof Archer) {
            System.out.println("you selected archer");
        } else if (chosenHero instanceof Warrior) {
            System.out.println("you selected warrior");
        } else {
            System.out.println("you selected NOTHING");
        }
    }

}

In Game.java, the code is meant to check whether chosenHero is an object of Archer.java, Warrior.java, or Mage.java, but I result with "you selected NOTHING". Why does instanceof fail to check if I already assigned it to Archer.java in the WelcomeScreen?

Answer 1

Because your constants are null. When you say,

private Archer archer;

it is equivalent to

private Archer archer = null;

Additionally, you have created three fields per instance. I think you wanted to do something like

private static final Hero archer = new Archer();
private static final Hero mage = new Mage();
private static final Hero warrior = new Warrior();

See also What does it mean to “program to an interface”?