Added new code for the article

immutables/src/main/java/com/reflectoring/io/immutables/basic/User.java

@@ -9,15 +9,15 @@ import java.util.List;
 @Value.Immutable
 public abstract class User {
 
-    abstract long getId();
+    public abstract long getId();
 
-    abstract String getName();
+    public abstract String getName();
 
-    abstract String getLastname();
+    public abstract String getLastname();
 
-    abstract String getEmail();
+    public abstract String getEmail();
 
-    abstract  String getPassword();
+    public abstract  String getPassword();
 
-    abstract List<Article> getArticles();
+    public abstract List<Article> getArticles();
 }

immutables/src/main/java/com/reflectoring/io/immutables/collections/CollectionsService.java

@@ -0,0 +1,46 @@
+package com.reflectoring.io.immutables.collections;
+
+import com.reflectoring.io.immutables.basic.Article;
+import com.reflectoring.io.immutables.basic.ImmutableArticle;
+import com.reflectoring.io.immutables.basic.ImmutableUser;
+import com.reflectoring.io.immutables.basic.User;
+
+public class CollectionsService {
+
+    public static void main(String[] args) {
+
+        Article article1 = ImmutableArticle.builder()
+                .id(0l)
+                .title("Lorem ipsum!")
+                .content("Lorem ipsum")
+                .userId(1l)
+                .build();
+
+        Article article2 = ImmutableArticle.builder()
+                .id(2l)
+                .title("Lorem ipsum!")
+                .content("Lorem ipsum")
+                .userId(1l)
+                .build();
+
+        Article article3 = ImmutableArticle.builder()
+                .id(3l)
+                .title("Lorem ipsum!")
+                .content("Lorem ipsum")
+                .userId(1l)
+                .build();
+        User user = ImmutableUser.builder()
+                .id(1l)
+                .name("Mateo")
+                .lastname("Stjepanovic")
+                .email("mock@mock.com")
+                .password("mock")
+                .addArticles(article1)
+                .addArticles(article2)
+                .build();
+        System.out.println(user);
+
+        user.getArticles().add(article3);
+
+    }
+}