Get parameter value from extended abstract class using 'Reflect'

I would like to get param2 value from a extended class that has common properties shared with an abstract class 'B' like this:

import java.lang.reflect.Field;

public class Fields {

    public class A{

        public abstract class B{
            int param1;
            String param2;
            public abstract void B ();
        }

        public class B0 extends B{
            @Override
            public void B() {
                this.param1 = 0;
                this.param2 = "Mario";
            }                                    
        }

        public class B1 extends B{
            @Override
            public void B() {
                this.param1 = 1;
                this.param2 = "Anna";
            }            
        }        

        B1 b1 = new B1();        

        public A (){
            b1.B();
        }

        public B0 GetB(Object AnyB){
            B0 tmp_b0 = (B0) AnyB;
            return tmp_b0;
        }
    }

    public Fields(){
        A a = new A();
        Field[] f = a.getClass().getDeclaredFields();

        for (int i = 0; i<f.length; i++){
            f[i].setAccessible(true);
            Object obj = f[i];
            String p2;
            p2 = a.GetB(obj).param2;
            System.out.println(p2);
        }        
    }

    public static void main(String [] args){
        Fields f = new Fields();        
    }
}

Formally the instruction B0 tmp_b0 = (B0) AnyB; is correct, but in runtime I get the error : Exception in thread "main" java.lang.ClassCastException: java.lang.reflect.Field cannot be cast to Fields$A$B0.

Why ?

There is a way to get the value of parameter param1 or param2.

There is a way ?

Thanks