HOW TO MAKE CLASS IMMUTABLE?
IMMUTABLE CLASS IS THE CLASS WHICH WE CANNOT CHANGE THE VALUES IF ONCE DEFINED IN THAT CLASS.
  THIS CAN BE ACHIEVED BY FOLLOWING WAY:
1.CREATING FINAL CLASS
2.DECLARING VARIABLES ONLY THROUGH CONSTRUCTORS
3.MEMBERS OF A CLASS SHOULD BE MADE WITH FINAL AND PRIVATE
4.DONT CREATE ANY SETTERS
5 DONT CREATE ANY METHODS THAT MODIFY MUTABLE CLASS
   LET US SEE AN EXAMPLE:

public final class FinalPersonClass {

      private final String name;
      private final int age;
     
      public FinalPersonClass(final String name, final int age) {
            super();
            this.name = name;
            this.age = age;
      }
      public int getAge() {
            return age;
      }
      public String getName() {
            return name;
      }
     
}