@Override
 public void Xuat() {
   super.Xuat();
   System.out.print("So san pham: " + this.soSanPham);
   System.out.print("So tien mot san pham: " + this.soTienMotSanPham);
   System.out.print("LUONG: " + this.TinhLuong());
 }
 // Xu ly nghiep vu
 @Override
 public void Nhap() {
   super.Nhap();
   Scanner scan = new Scanner(System.in);
   System.out.print("Nhap so san pham: ");
   this.soSanPham = Integer.parseInt(scan.nextLine());
   System.out.print("Nhap so tien mot san pham: ");
   this.soTienMotSanPham = Integer.parseInt(scan.nextLine());
 }