Which one is not a necessary condition for constructors

It is treated as a special member function because its name is the same as the class name . Java constructors are invoked when their objects are created. It is named such because, it constructs the value, i.e., provide data for the object, i.e., they are used to initialize objects.

will a compiler generated constructor/empty constructor always be called when you instantiate an object? No. If your class is a so-called “POD” (plain old data) then the compiler-generated constructor won’t always be called .

In class-based object-oriented programming, a constructor (abbreviation: ctor) is a special type of subroutine called to create an object . It prepares the new object for use, often accepting arguments that the constructor uses to set required member variables.

This is because when you do the following: obj2 = 100 ; this one will first call abc(int x) to generate an object of the class, then call the default copy assignment operator (since no user-defined is provided) to assign the value 100 to existing obj2 . After the assignment, the temporary object is destructed.