He differentiates between strong immutability (class is made final) and weak immutability (methods are individually and explicitly declared final rather than declaring class final).

Ensure a variable is unchanged within a method. When Java’s static and final keywords are combined, a class-level variable can be made constant, which essentially turns it into a global variable. This ...

The availability of ReflectiveOperationException in Java 7 is a specific exception parent class that can be caught to handle all its child reflection exception classes in a single catch.