Technique used in java to make string immutable?

Question

Technique used in java to make string immutable?
or how can i make my string class immutable.
I just want to know the logic behind this.

Answer 1

In Java, String objects are already immutable.

I can't speak to how the Java language creators specifically made String immutable, but here are some guidelines that you can follow to make your own classes immutable:

1. Don't use setter methods.
2. Make all fields private and final.
3. Don't allow methods to be overwritten (either make class final or use a factory pattern).
4. If any fields are objects of mutable type, take care when using those objects: Defensively clone them when returning those objects off of a getter method or receiving them in the constructor, and don't provide methods which modify the mutable objects.