Subclasses With Unique Static Variables

Say I have a class called ClassA which I want to hold my data. Now inside ClassA want to hold instances of a class lets call ClassB. So far we are here.

import blah.B
public class A {
private B myB;
(Getters setters etc)
public String getBString() {
B.getString();
}
}

However I want to have multiple extensions of ClassB which have UNIQUE static variables.

public class B-1 extends B {
private static String mString;
private static int mInt;
}

The problem I have run into is I can't have subclasses with their own static variables. I need the A class to hold any type of B class. How can I manage this?meant

public String getBString{
return B.getString();
}