Must implement specifik interface

Question

Hi,
Im creating a game to force myshelf to code a game-engine, just for fun. In this game I have superclass for a basic unit. This class gets subclassed down to game-units. I have different type of game units, some more advanced than others (my game idea is like a manager game where choose between units similar to warcraft 3 units).
To help the game-engine separate between the different type of units and the methods that can be used on them, I want to use differtent interface for the advanced units. This could be the start of the Wizard-class:
public class Wizards extends BasicUnit implements SpellCaster {
// method and variables that are specific for a wizard and dont excist in BasicUnit
}Question is: How can I force a method in the game-enginge class to look if a used unit implements a certain interface, in this case the SpellCaster-interface?
I know it should be possible, like the Comparable Interface. But how do i do it?
If its a dumb question a link to the specifik documents would do, I read it myshelf. But of course I would be happy if someone have the kindness to write an example. Again, this aint homework, just a fun x-mas project for me.

Answer 1

Ani_Skywalker wrote:
Hi again Jverd,
I google [visitor pattern|http://en.wikipedia.org/wiki/Visitor_pattern] and through that I also find [virtual function|http://en.wikipedia.org/wiki/Virtual_functions] . I can see how its usefull in this issue.
Thought my main concern for the moment is about [composition over inheritance|http://blogs.msdn.com/steverowe/archive/2008/04/28/prefer-composition-over-inheritance.aspxI]. This is not what we learned in school when I took my first and second java courses. But I think the composition over inheritance strategy seems very sensible.
jverd wrote:
I don't really know your whole picture, but one option is to define a type that has those particular operations in common, and pass that type around when that's what you need. The subclasses could inherit from a base class that provides those, or implement an interface, and then add their own methods.But this is exactly what my class BasicUnit does. Maybe my english is bad and I misslead you, or maybe I should pick a better name for that class, like Unit. But what it does is to hold methods that every unit in the game use. Subclasses that need more methods adds that. The way you wrote your example is kind of how I've done it, as it seems to me. Could you tell me were you think I do wrong?It may have just been a misunderstanding on my part, as I don't know you and I don't know your requirements or the details of how you're implementing them.
Or it may be that you're kind of close to doing it correctly, but not quite. The situation I described as a good approach can look a lot like the not-so-good way I thought you were doing it. I'm kind of sleep-deprived right now, so I don't have the energy or brainpower to go into any more detail at the moment.
Good luck though. I expect somebody will continue helping you if you keep working at it.