public int compareTo(Osoba other)
    {
        Student otherStudent = (Student) other;
        
        if(this.sredniaOcen<otherStudent.sredniaOcen)
            return super.compareTo(other);
        else if(otherStudent.sredniaOcen<this.sredniaOcen)
            return super.compareTo(other);
        return super.compareTo(other);
        
        //Student otherStudent = (Student) other;
        //return Double.compare(this.sredniaOcen, otherStudent.sredniaOcen);
    }