public void SinhVien(String _tenSV, int _maSV, float _diemToan, float _diemLy, float _diemHoa){
        this.tenSV = _tenSV;
        this.maSV = _maSV;
        this.diemToan = _diemToan;
        this.diemLy = _diemLy;
        this.diemHoa = _diemHoa;
    }