Spring Boot Add Data from different classes

[Eleni Pap]

Hallo everyone,

I would like to complete a program on Java with Spring Boot. I have a mini problem.
I use two different tables on my sql table, one for price one for discount.

I would like to calculate the price on ProductService, by substract the row of column of another Class, the class of ProductDiscount,for example.

So,
I have two tables in sql for price  and for discount .There are specific column, which is used to calculate  at each class .
On the total price I should calculate the final price. It is essential to use another class to add or multiple.




Is it possible? Are there any examples, I cannot find something similar in the web, add or substract data from different classes.

[Eleni Pap]

@Entity

@Table(name = "repo")

public class Repo {



    @Id

    @GeneratedValue(strategy = GenerationType.IDENTITY)

    @Column(name = "id")

    Long id;



    @Column(name="stock")

    private Long stock;

}



@Entity

@Table(name = "voucher")

public class Voucher {

    @Id

    @GeneratedValue(strategy = GenerationType.IDENTITY)

    @Column(name = "id")

    private Long id;





    @Column(name = "quantity")

    private BigDecimal quantity;
 
 
@Column(name = "type")

private boolean type;
 


}


@Service
public class VoucherService{
    @Override
    
    public Voucher dtoToEntity(VoucherDTO dto) {
    
        Voucher voucher = new Voucher();
    
        voucher.setId(dto.getId());     
    
        voucher.setDescription(dto.getDescription());
 
        
    
    
    
    List<VoucherProduct> voucherList = new ArrayList<>();
    
        for (VoucherProductDTOMini inv : dto.getVoucherproducts())
    
    
    
            VoucherProduct voucherL=voucherProductService.DTOtoEntity(inv);
    
            voucherList.add(voucherL);
    
        }
    
        voucher.setVoucherproducts(voucherList);
    
        return voucher;
    
    }
 
    
@Override

public VoucherDTO createVoucher(VoucherDTO voucherDTO){

    Voucher voucher=new Voucher();



     voucher=voucherRepository.save(voucher);



    VoucherDTO voucherDTOnew=new VoucherDTO(voucher);



    return voucherDTOnew;



}

i  should check the type of my voucher (true) , and I should add on my repo entity at stock.

In which way can I update the two entities at the same time?

When I add a true voucher, I should add on my repo.stock the data of voucher.quantity

Could anyone help me?