what final keyword do in java and how to use it

final classes
---
any class that defines final will not be subclassed.

you can not extends any class from a final class.


final methods
---
any method that defines final will not be overriden.

you can not override final methods.


final variables
---
final variables initiated only once.

if you define setter for a final variable, you will get a compile time error from the compiler.