使用 Java 8 生成 dto 列表到实体列表

Question

I'm new to Java. I have list of dto objects and I need to convert it to the list of entities by iterating through dtos list.

I should not use model mapper or MapStruct or BeanUtils. I need to do this in the Java way, and I'm not sure how to iterate both lists at the same time.

public class AddressDto {
    private String unitNo;
    private String floorNo;
    private String buildingName;
    private String areaName;
    //getters and setters
    }
public class AddressEntity {
    private String unitNo;
    private String floorNo;
    private String buildingName;
    private String areaName;
    //getters and setters
    }

public void getAddress() {
        
        List<AddressDto> addressDtoList=new ArrayList<>();
        addressDtoList.add(new AddressDto("174", "7", "Grove", "BR"));
        
        List<AddressEntity> addressEntityList=new ArrayList<>();
        addressEntityList.add(new AddressEntity("28", "13", "Green", "Tampa"));
        
        List<AddressEntity> addressEntityListResult=convertDtoToEntity(addressDtoList);
        
    }
    
    private List<AddressEntity> convertDtoToEntity(List<AddressDto> aDto) {

        List<AddressEntity> newAddressEntityList = null;

        for (AddressDto dto : aDto) {

          //Generate and Return the newAddressEntityList by replacing Green with Grove and BR with Tampa
        }

        return newAddressEntityList;
    }

It should be replacing Green with Grove and BR with Tampa only. Remaining object such as "28", "13" should be unchanged.

Answer 1

Nowadays, the Java way is to use Stream API .

Here's a snippet on how to convert a List<AddressDto> to a List<AddressEntity>

  private static List<AddressEntity> convertDtoToEntity(List<AddressDto> aDto) {
    return aDto.stream()
        .map(dto -> new AddressEntity(dto.getUnitNo(), dto.getFloorNo(), dto.getBuildingName(), dto.getAreaName()))
        .collect(Collectors.toList());
  }

The function passed to the .map method is the one responsible of converting each element of the stream from AddressDto to AddressEntity.

Answer 2

You have received a great answer, but here's another way to do it:

private List<AddressEntity> convertDtoToEntity(List<AddressDto> aDto) {
    List<AddressEntity> newAddressEntityList = new ArrayList<>();

    for (AddressDto dto : aDto) {
        AddressEntity addressEntity = new AddressEntity(
                dto.getUnitNo(),
                dto.getFloorNo(),
                dto.getBuildingName(),
                dto.getAreaName()
        );
        
        newAddressEntityList.add(addressEntity);
    }

    return newAddressEntityList;
}