Why is it mandatory to have private Constructor inside a Singleton class

Question

This is my singleton class for obtaining the database connection.

I have a question here: why it compulsory to have a private constructor inside a singleton class (a

Answer 1

The comment as you said that If I am complete owner of my application and I will never commit mistake of creating instance of singleton class directly using the public constructor but will use the static method for getting it. But in real world, often application switch hands between multiple developers. If the new developer is not aware that you want only one instance of the class in the application, he/she may accidently create another one by using the public constructor.