added concept of final keyword

java/more/final-keyword.md

@@ -0,0 +1,65 @@
+## Final Keyword in JAVA
+
+Final keyword in java is a non-access modifier. It is used to restrict user from making any change in variable, method and classes.
+
+### 1. Final Variable
+If any variable is declared with keyword final, then the value of final variable can't be change, i.e. it becomes constant.
+
+### Example
+
+```java
+class Student{
+    //final variable
+    final int id=50;
+    void get_id(){
+        id=100;
+    }
+    public static void main(String[] args){
+        Student obj=new Student();
+        obj.get_id();
+    }
+}
+```
+
+### 2. Final Method
+If any method is declared with keyword final, then it can't be overridden.
+
+### Example
+
+```java
+class Fruit{
+    //final method
+    final void run(){
+        System.out.println("Inside Fruit Class");
+    }
+}
+class Apple extends Fruit{
+    void run(){
+        System.out.println("Inside Apple Class");
+    }
+    public static void main(String[] args){
+        Apple obj=new Apple();
+        obj.run();
+    }
+}
+```
+
+### 3. Final Class 
+If any class is declared with keyword final, then it can't be inherited.
+
+### Example
+
+```java
+//final class
+final class Fruit{
+}
+class Apple extends Fruit{
+    void run(){
+        System.out.println("Inside Apple Class");
+    }
+    public static void main(String[] args){
+        Apple obj=new Apple();
+        obj.run();
+    }
+}
+```