Why do finalized classes in java sources have private constructors?

Question

Java

In the course of learning the language, I discovered the source codes and plunged headlong into them. Now I'm looking at the Math class and StrictMath. I noticed that both (and many others) have a private constructor and an interesting comment.

/*
 * Don't let anyone instantiate this class.
 */
private Math() {}

Why did they do it? Why is creating an instance of, for example, the StrictMath class bad?

Answer 1

Because these classes are not classes in general. They are made classes solely due to the fact that in Java you cannot write any code outside the class. These utility classes are essentially namespaces for pure functions (static methods). It is pointless to create their instances, and therefore it is forbidden.

Answer 2

Nothing special. It's just that library functions protect against "abnormal" use more strongly.