Why String is Immutable ?

Why String is immutable and final in Java?

 

when you define a string object . object creates in heap . value of this object can not be change. String

 str=new String("Shiv"); now str.concat("shakti"); if you print str . Output will be Shiv only. Not Shivshakti.

 But when you write str=new String("shakti"); print output will be shakti. This happens due to str change 

of reference to shakti object . Now if you write str=str.concat("shakti"); Output will be Shivshakti. This is

happens due to change reference but str value remains same Shiv. In case of shakti it create new object in heap.