#117 resolve last discussion

src/main/java/ru/ulstu/grant/service/GrantService.java

@@ -154,26 +154,23 @@ public class GrantService {
     public List<User> getGrantAuthors(GrantDto grantDto) {
         List<User> filteredUsers = userService.filterByAgeAndDegree(grantDto.isHasAge(), grantDto.isHasDegree());
         if (grantDto.isWasLeader()) {
-            filteredUsers = filteredUsers
-                    .stream()
-                    .filter(getCompletedGrantLeaders()::contains)
-                    .collect(toList());
+            filteredUsers = checkContains(filteredUsers, getCompletedGrantLeaders());
         }
         if (grantDto.isHasBAKPapers()) {
-            filteredUsers = filteredUsers
-                    .stream()
-                    .filter(getBAKAuthors()::contains)
-                    .collect(toList());
+            filteredUsers = checkContains(filteredUsers, getBAKAuthors());
         }
         if (grantDto.isHasScopusPapers()) {
-            filteredUsers = filteredUsers
-                    .stream()
-                    .filter(getScopusAuthors()::contains)
-                    .collect(toList());
+            filteredUsers = checkContains(filteredUsers, getScopusAuthors());
         }
         return filteredUsers;
     }
 
+    private List<User> checkContains(List<User> filteredUsers, List<User> checkUsers) {
+        return filteredUsers.stream()
+                .filter(checkUsers::contains)
+                .collect(toList());
+    }
+
     private List<User> getCompletedGrantLeaders() {
         return grantRepository.findByStatus(Grant.GrantStatus.COMPLETED)
                 .stream()