IntelliJ IDEA: Generating Immutable Classes and Fields

PROBLEM

By default, IntelliJ IDEA generates mutable classes and fields.

One of the steps to achieve immutability is to make all classes and fields to be final.

SOLUTION

Making Fields Final

Go to Preferences… -> Code Style -> Java -> Code Generation tab

Under Final Modifier, check both Make generated local variables final and Make generated parameters final.

Making Classes Final

Go to Preferences… -> File and Code Templates -> Templates tab

Select Class and add final.