Question

In my game, all game objects extend an Entity class. All enemy objects have their own class which extend Enemy. Enemy extends Entity.
In other words,
Entity -> Enemy -> SharkEnemy.

Now, I want to have a function to let me test for collision against a specific class.
That is, if for example I have a bullet class, I want it to only test for collision against entities that extend Enemy.

I’ve googled around and this is what I have:

public <T> Entity collide(Entity a, Class<T> desiredClass)
{

    for (Entity b : entities)
        if (b.getClass() == desiredClass && collide(a, b))
            return b;
    return null;
}

That is kind of what I want, but I need to know if it extends desiredClass, not if the class equals desiredClass.

Answer 1

Instead of checking for class equality, use Class.isAssignableFrom()

 public <T> Entity collide(Entity a, Class<T> desiredClass)
 {

     for (Entity b : entities)
         if (desiredClass.isAssignableFrom( b.getClass() ) && collide(a, b))
             return b;
     return null;
 }