creating a list with multiple properties - entity from DTO

Question

I haven't added the getter and setter for simplicity. I'm facing a mapping issue here. I want to achieve this using java stream.

public class P{
     private ArrayList<Lin> lin;
}

public class Lin{
    private Oh oh;
    private ArrayList<Pr> pr;
    private ArrayList<Qty> qty;
}

public class Oh{
    private int ohId;
    private String size;
}

public class Pr{
   private int prId;
   private String sys;
}

public class Qty{
   private int qtyId;
   private String older;
}

With the above P class I want to convert a entity in the below structure,

public class OrderLi{
    private int ohId;
    private String size;
    private ArrayList<Pr> pr;
    private ArrayList<Qty> qty;
}

I want to convert this using java stream without adding repeated loops.

Answer 1

From what I understand, you want to convert from a P to list of OrderLi, here is my solution.

final List<OrderLi> orderLiList = p.getLin()
    .stream()
    .map(
        lin -> new OrderLi(
            Optional.ofNullable(lin.getOh()).map(Oh::getOhId).orElse(0),
            Optional.ofNullable(lin.getOh()).map(Oh::getSize).orElse(null),
            lin.getPr(),
            lin.getQty()
        )
    )
    .collect(Collectors.toList());