[Java/en] Adding a reference for treemap (#2300)

* Adding a reference for treemap

Adding reference for a treemap

* Removing my name from the contributors list

Removing my name from the contributors list as it requires a significant contribution to add my name to it.

java.html.markdown

@@ -232,6 +232,9 @@ public class LearnJava {
         //            interface. This allows the execution time of basic
         //            operations, such as get and insert element, to remain
         //            constant even for large sets.
+        // TreeMap - This class is a sorted tree structure. It implements a red
+        //           black tree and sorts the entries based on the key value or
+        //           the comparator provided while creating the object
 
         ///////////////////////////////////////
         // Operators