Just Make the class as a final

dont provider setters and provide the parameter constructor

create a class , having some private variables and setter 
method for that variable , In constructor pass the 
arguments to set this variable.

To make a class immutable, 
1. Don't provide any methods that modify the object.
2. Ensure that no methods may be overridden. Mark the class 
as final. Make all fields final and private.

1. Mark the class as 'final' to avoid any 
subclassing/overriding
2. Make the fields as 'private' & 'final' to avoid 
reassining in any way after creation of the object by 
passing params via contructor

1.Mark the class as final to avoid subclass, So subclass 
can't change any thing in super class.
2. When ever you are chaning any property of that class 
make a new instance of that calss.
e.g public modify(Object obj0)
{ 
ClassName a =new ClassName ();
a.modify()// modification logioc
}