diff --git a/tech/Java.wiki b/tech/Java.wiki
index 0db4998..dfbe09d 100644
--- a/tech/Java.wiki
+++ b/tech/Java.wiki
@@ -5,11 +5,33 @@ can run on almost anything.
 
 == Data structures ==
 
-| C++ DS | Java DS   | Notes                      |
-| Vector | ArrayList | Threadsafe                 |
-| Vector | Vector    | Not threadsafe; deprecated |
-| Deque  | Deque     |                            |
-| List   | ArrayList | Both linked lists          |
-| 
+| C++ DS        | Java DS   | Notes                                       |
+| Vector        | ArrayList | Threadsafe                                  |
+| Vector        | Vector    | Not threadsafe; deprecated                  |
+| Deque         | Deque     |                                             |
+| List          | ArrayList | Both linked lists                           |
+| Map           | TreeMap   | Red-black tree                              |
+| Set           | TreeSet   | Red-black tree                              |
+| unordered_set | Hashset   | Hashtable                                   |
+| unordered_map | Hashmap   | Non blocking but race conditions can occour |
+| unordered_map | Hashtable | Threadsafe but blocking; deprecated         |
+
+
+
+
+== Classes ==
+
+=== Constructor ===
+
+{{{
+    public class MyClass{
+        public MyClass(){
+            //constructor code here
+        }
+        
+        
+    }
+  }}}
+