how to make constructor definition mandatory
<p>I have an interface I that is implemented by a base class B. The base class is extended by a bunch of classes (A,C,D) that must init some of the protected vars declared in base class B. I'd like to make the declaration of a constructor mandatory in the subclasses (A,C,D), to discourage the user from relying on default constructor that's declared in B. Yet I <em>do</em> want the B's default constructor to execute automatically, since B can be used by itself as well. How can I accomplish this?</p>

<p>thanks</p>
