How to create immutable class in java?
1) Declare the class as final so it can’t be extended.
2) Make all fields private so that direct access is not allowed.
3) Don’t provide setter methods for variables.
4) Make all mutable fields final so that its value can be assigned only once.
5) Initialize all the fields via a constructor performing the deep copy.
6) Perform cloning of objects in the getter methods to return a copy rather than returning the actual object reference.
