java stream

Group by

public List<RegionPayload> getAllRegions() {
  List<RegionPayload> result = new ArrayList<>();
  List<Region> allRegion = regionRepository.findAll();
  Map<String, List<Region>> regionMap =
      allRegion.stream().collect(Collectors.groupingBy(Region::getRegion));
  for (Map.Entry<String, List<Region>> elem : regionMap.entrySet())
    result.add(new RegionPayload(elem.getKey(), elem.getValue()));
  return result;
}

import com.lge.cdp.model.Region;
import java.util.List;
import lombok.AllArgsConstructor;
// import lombok.ToString;
import lombok.Getter;
import lombok.Setter;

@Getter
@Setter
@AllArgsConstructor
// @ToString
public class RegionPayload {

  private String region;
  private List<Region> countryList;
}