fix lambda

src/main/java/ru/ulstu/conference/model/ConferenceDto.java

@@ -3,6 +3,7 @@ package ru.ulstu.conference.model;
 import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import org.springframework.format.annotation.DateTimeFormat;
+import ru.ulstu.core.model.BaseEntity;
 import ru.ulstu.deadline.model.Deadline;
 import ru.ulstu.paper.model.Paper;
 
@@ -88,8 +89,8 @@ public class ConferenceDto {
         this.beginDate = conference.getBeginDate();
         this.endDate = conference.getEndDate();
         this.deadlines = conference.getDeadlines();
-        this.userIds = convert(conference.getUsers(), user -> user.getId());
-        this.paperIds = convert(conference.getPapers(), paper -> paper.getId());
+        this.userIds = convert(conference.getUsers(), BaseEntity::getId);
+        this.paperIds = convert(conference.getPapers(), BaseEntity::getId);
         this.users = conference.getUsers();
         this.papers = conference.getPapers();
     }