EDIT: Try to fix server, again

src/Client/src/main/java/greenify/client/rest/UserService.java

@@ -99,6 +99,26 @@ public class UserService {
         return this.restTemplate.getForObject(builder.build().encode().toUri(), UserDto.class);
     }
 
+    /**
+     * a user adds vegan meal.
+     * @param id the id of the user
+     * @param name the username of the user
+     * @return a userDTO
+     */
+    @SuppressWarnings("Duplicates")
+    public UserDto addFriend(Long id, String name, String friend) {
+        //this method is almost the same as the registerUser one, but with a different link
+        HttpHeaders headers = new HttpHeaders();
+        headers.set("Accept", MediaType.APPLICATION_JSON_VALUE);
+        UriComponentsBuilder builder = UriComponentsBuilder.fromHttpUrl("http://localhost:8080/addFriend")
+                .queryParam("id", id)
+                .queryParam("name", name)
+                .queryParam("friend", friend);
+        HttpEntity<?> entity = new HttpEntity<>(headers);
+        System.out.println(builder.build().encode().toUri());
+        return this.restTemplate.getForObject(builder.build().encode().toUri(), UserDto.class);
+    }
+
     @RequestMapping("/userData")
     public int getVeganData(@RequestParam(value = "veganMeal") int veganMeal) {
         return veganMeal;

src/Server/src/main/java/greenify/server/data/model/User.java

@@ -111,14 +111,27 @@ public class User {
         }
     }
 
+    public String friendsToString(){
+        String result = "";
+        for(User u : friends){
+            result += u.getId() + ", ";
+        }
+        result = result.substring(0, result.lastIndexOf(","));
+        return result;
+    }
+
     /**
      * Returns a human readable object. It's in JSON.
      * @return the JSON form of the object.
      */
     @Override
     public String toString() {
-        return "User(id=" + this.id + ", name=" + this.name + ", password="
-                + this.password + ", veganMeal=" + this.veganMeal + ")";
+        String result = "User(id=" + this.id + ", name=" + this.name + ", password="
+                + this.password + ", veganMeal=" + this.veganMeal + ", friends=[";
+        result += friendsToString() + "])";
+
+//                result += ")";
+                return result;
     }
 
     @Override

src/Server/src/test/java/greenify/server/data/model/UserTest.java

@@ -27,6 +27,7 @@ public class UserTest {
         assertEquals(user.getPassword(), "password");
         assertEquals(user.getVeganMeal(), 3);
         assertEquals(user, testUser);
+        assertEquals(user.getFriends(), new ArrayList<User>());
     }
 
     @Test
@@ -100,5 +101,25 @@ public class UserTest {
         });
         assertEquals(user.getFriends(), new ArrayList<User>());
     }
+
+    @Test
+    public void JsonTest(){
+        User user = new User(1l, "user", "friends", 0);
+        User friend = new User(2l, "friend", "friends", 0);
+        assertEquals(user.getFriends(), new ArrayList<User>());
+        user.addFriend(friend);
+        ArrayList<User> list = new ArrayList<User>();
+        list.add(friend);
+        assertEquals(user.getFriends(), list);
+        System.out.println(user.toString());
+    }
+
+    @Test
+    public void friendsToStringTest(){
+        User user = new User(4l, "user", "pass", 0);
+        User friend = new User (5l, "friend", "pass", 0);
+        user.addFriend(friend);
+        System.out.println(user.friendsToString());
+    }
 }