avoid instanceof in Java

Question

I have been told at some stage at university (and have subsequently read in upteen places) that using instanceof should only be used as a \'last resort\'. With this

Answer 1

I learned about Visitor pattern in Compiler class at university, I think it might apply in your scenario. Consider code below:

public class GameObjectVisitor {

    public boolean visit(GameObject1 obj1) { return true; }
    .
    .
    // one method for each game object
    public boolean visit(GameGroup obj1) { return true; }
}

And then you can put a method in GameObject interface like this:

public interface GameObject {

    .
    .
    public boolean visit(GameObjectVisitor visitor);
}

And then each GameObject implements this method:

public class GameGroup implements GameObject {

    .
    .
    .
    public boolean visit(GameObjectVisitor visitor) {
        visitor.visit(this);
    }
}

This is specially useful when you've complex inheritance hierarchy of GameObject. For your case your method will look like this:

private void allocateUITweenManager() {

    GameObjectVisitor gameGroupVisitor = new GameObjectVisitor() {
        public boolean visit(GameGroup obj1) {
            obj1.setUITweenManager(mUITweenManager);
        }
    };

    for(GameObject go:mGameObjects){
      go.visit(gameGroupVisitor);
   }
}