Final Keyword In Java : Introduction

• Java final keyword is used as prevention, i.e. it restricts user.
• Java final keyword has three uses :
  1. It can be used with variables to prevent their values from being changed.
  2. It can be used to prevent overriding.
  3. It can be used to prevent inheritance.

Final Keyword In Java : The Discussion

1. final with Variables

   • If any variable is made final , it restricts the user to changes its value i.e. the content of variable cannot be changed.
   
   

   Note :  A blank variable can also be declared as final and it will be initialized in constructor only, because constructor are invoked as soon as object of that class is created.

   
   Example
   Final With Variable : Example
   
   Final With Variable : Output
   
   • We tried to change the final variable and compiler throws an error which is stated in output.
   
   

2. final with Method

   • The only purpose of using final with method is to prevent method overriding.
   • When a method is declared as final then it cannot be overridden. If we try to do so , we get a compile time error. Let us understand with an example.
   
   Example
   
   Final With Method : Example
   
   Final With Method : Output
   
   • In the above images, We tried to override a final method and got an error.
   
   

3. final with Class

   • A class preceded with final keyword cannot be inherited.
   • Final keyword prevents a class from getting inherited and also implicitly declares all of its methods as final.
   
   Example
   
   Final With Class : Example
   
   Final With Class : Output