Why might one also use a blank constructor?

Question

I was reading some Java recently and came across something (an idiom?) new to me: in the program, classes with multiple constructors would also always include a blank constr

Answer 1

That is NOT a copy constructor. Basically you want empty constructors when working with some framework. Shall there always be an empty constructor, of course, public or private, but at least it allows you to keep control of how the class is being (or not) instantiated.