How can constructors be private?

Answer 1

usually those are used for friend classes.

Answer 2

Vaibhav https://www.geeksforgeeks.org/can-constructor-private-cpp/

Answer 3

hinanawi please explain it further.

Answer 4

you make constructor private when you don't want it to be used to create the object from outside without control.
so only a friend class or a public class method of that class can be used to create a new instance, and can do some checks first.
Example: if you want to ensure there is only one instance of that class, you can have a class variable as a counter, and a class method "create" that calls the constructor and returns the object only if the counter is null;