Is it mandatory utility class should be final and private constructor?

Question

By making private constructor, we can avoid instantiating class from anywhere outside. and by making class final, no other class can extend it. Why is it necessary for Util clas

Answer 1

It's not necessary, but it is convenient. A utility class is just a namespace holder of related functions and is not meant to be instantiated or subclassed. So preventing instantiation and extension sends a correct message to the user of the class.