Final Keyword In Java

Final -> Read Only
Assigned value once and only once, Can be used with  variables , methods and Evern Classes.
Final Variables:
A final variable can be assigned value  once at the time of declaration and cannot be re-assign value.

Code Example:


  

package com.aurangzeb.utk;

public class FinalVariable {

     

      // No error declared and initialzed

      public final int a_final=10;

     

     

      // The blank final field b_final may not have been initialized

      // variables must be initialzed at the time of declaration.

     

     

      public final int b_final;

      public int c;

     

      public void finalVariable(){

           

           

            // Error cannot re-assign value to a final variable

           

            a_final =5;

            // can assign value to a non final variable

            c=10;

      }

     

     

}

Final Methods: 

Cannot override the method , cannot override any different Implementation 

Example Code:

package com.aurangzeb.utk;

public class FinalMethod {

      final void cannotOverride(){

           

            System.out.println("Cannot override :Final method");

      }

     

     

     

      // Illegal combination of modifiers abstract and final, a method cannot be both final

      //and abstract

      public final abstract void abstractMethod();

      }

     

     

}

 class child extends FinalMethodClass{

       

       // Error Cannot override a final method

       

       void cannotOverride(){

             

       }

 }

Final Class:

Cannot extends the class, e.g cannot add/modify anything in the class

Appear as a leaf in the Inheritance hierarchy.

Example Code:

 

package com.aurangzeb.utk;

public final class FinalClass {

      public void myMethod(){

           

            System.out.println("A method in the final class");

      }

     

}

class child extends FinalClass{

     

      // compile Time Error cannot inherit from a Final Class

}