import java.util.*;
import java.util.stream.*;

class Ideone {
  public static void main(String[] args) {
    final List<EntityClass> queryResultList = List.of(
        EntityClass.of(13),
        EntityClass.of(1337),
        EntityClass.of(42));
    final String delimiter = ", ";
    System.out.println(queryResultList.stream()
        .map(EntityClass::getId)
        .map(Object::toString)
        .collect(Collectors.joining(delimiter)));
  }
}

class EntityClass {
  private final int id;

  private EntityClass(int id) {
    this.id = id;
  }

  public static EntityClass of(int id) {
    return new EntityClass(id);
  }

  public int getId() {
    return id;
  }
}