add class, function and interface naming convention

Author: anishmanandhar

docs/java/classes.md

@@ -5,3 +5,9 @@ sidebar_label: Classes
 ---
 
 #### The following convention should be followed for `class` naming:
+
+* Class names are generally nouns, in title-case with the first letter of each separate word capitalized. e.g.
+    - **LeaveController**
+    - **EmployeeRepository**
+    - **AttendanceRecord**
+  

docs/java/functions.md

@@ -1,7 +1,27 @@
 ---
 id: functions
-title: Functions and Methods
+title: Functions 
 sidebar_label: Functions
 ---
 
-#### The following convention should be followed for `def` naming:
+#### The following convention should be followed for `function` naming:
+
+* Method names should contain a verb, as they are used to make an object take action. They should be mixed case, beginning with a lowercase letter, and the first letter of each subsequent word should be capitalized. Adjectives and nouns may be included in method names:
+
+### verb
+```
+public int calculateRemainingLeaves() {
+
+    //implementation
+
+} 
+```
+
+### verb and noun
+
+```
+public String getFullName() {
+    
+    //implementation
+}
+````

docs/java/interfaces.md

@@ -10,3 +10,8 @@ sidebar_label: Interfaces
 * Generally, should be **adjectives** or **nouns**
   - *LeaveService*
   - *Approvable* 
+
+* Interface represents type or contract on what the public methods and properties have to support. While naming interface, make sure its implementating classes demonstrate a subset behavior.
+  e.g
+    - **HealthCheckService** interface can have implementing classes like **DBHealthCheckService** , **StorageHealthCheckService**, **NotificationHealthCheckService**
+    - Try not to includes Prefix like **I** or suffix like **impl**