java partial classes

Question

Small preamble. I was good java developer on 1.4 jdk. After it I have switched to another platforms, but here I come with problem so question is strongly about jdk 1.6 (or h

Answer 1

How about that: 
Compute.java  =    your class
Compute$.java  =   base class for partial classes. Reference a Compute object
Compute$Add.java = your partial class. Subclass Compute$.
Compute$Sub.java = your partial class. Subclass Compute$.

file Compute.java

public class Compute {
    protected int a, b;
    Compute$Add add;
    Compute$Sub sub;

    public Compute() {
        add = new Compute$Add(this);
        sub = new Compute$Sub(this);
    }

    public int[] doMaths() {
        int radd = add.add();
        int rsub = sub.sub();
        return new int[] { radd, rsub };
    }
}

file Compute$.java

public abstract class Compute$ {
    protected Compute $that;
    public Compute$(Compute c){
        $that=c;
    }
}

file Compute$Add.java

public class Compute$Add extends Compute$ {
    public Compute$Add(Compute c) {
        super(c);
        // TODO Auto-generated constructor stub
    }

    public int add(){
        return $that.a+$that.b;
    }
}

file Compute$Sub.java

public class Compute$Sub extends Compute$ {
    public Compute$Sub(Compute c) {
        super(c);
    }

    public int sub() {
        return $that.a - $that.b;
    }
}