ES java

public class Frutto {
   public String toString(){return "Frutto";}
   public void macedonia(Frutto f){System.out.println(this + " - " + f);}
   public void confronta(Frutto f){System.out.println("Sono uguali");}
}
public class Mela extends Frutto {
   public String toString(){return "Mela";}
   public void macedonia(Mela f){System.out.println(this + " - " + f);}
   public void confronta(Mela m){System.out.println("Sono diversi");}
}
public class Arancia extends Frutto {
   public String toString(){return "Arancia";}
   public void macedonia(Arancia f){System.out.println(this + " - " + f);}
   public void confronta(Arancia a){System.out.println("Non ho idea");}
}


public class Test {
   public static void main(String args[]) {
    Frutto f1, f2;
    Mela m;
    Arancia a;
    f1 = new Mela();
    f2 = new Arancia();
    m = new Mela();
    a = new Arancia();
    f1.macedonia(f2);
    f1.confronta(f2);
    a.confronta(f2);
    a.confronta(m);
    f2 = m;
    f1.macedonia(f2);
    a.macedonia(m);
    a.confronta(a);
    }
}