Java Question

steviec

I'm currently in the planning process for a program I'm going to be working on and there's one thing that I'm a bit confused about, wondering if anyone could point me in the right direction.

Game calculates stuff
Game sends AI information
AI returns decision
Repeat

What the game does isn't important, and if I was just hardcoding my AI I'd know exactly what I was doing, but here's the catch. I want it to support user-written AIs. But those AIs should never be hard coded into my program or effect anything.

I want something like:
User writes myAI.java (inheriting from masterAI that is hardcoded into my program perhaps?)
User compiles myAI.class
User runs program
Game sends masterAI information
User goes to menu in program, picks to load 'myAI.class'
Game now sends myAI information.


I figure it's possible, I'm just not very object orientated. is it possible to essentially swap in different classes (using inheritence/interfaces?) that have the same methods but do them in different ways, via a menu within the program?

Thordon

Its definetely possible, have a look at RoboCode, its a java game where you write AI code for a tank, and then have your tank fight other peoples self coded tanks, there might some explanation of how it works listed on their site somewhere.

http://robocode.sourceforge.net/

You might have to use the reflection AI to dynamically cast a class to a certain subclass, Im not too sure how I would go about it myself.

aidan_walsh

You could make sure that the myAI class extends a predefined interface, and use a ClassLoader.

MrPinK

If you look for a tutorial on the Java Reflection API that'll give you a good start on handling classes dynamically, but that basics of it should be something like:
- Load the user class
- Check if it implements the required interface
- Create an instance of the class
- Return the instance to Game for it to use.

steviec

Ok I'll look into that thanks a lot

Syth

The java reflection stuff is exactly what you want. I'm working on it right now. I need to be able to load and analyse classes that are specified on the command line.

Look into java.lang.Class class and Class.forName(String className) method, it returns a java.lang.Class that represents that class. You can also do funky things with Method invocation, but that'd be a bit beyond your needs. You can invoke constructors for that class to get a new instance of it.