title: Can we stop the run of a constructor?
body: <p>I need to create an object of some type.
  The class of the object has just one constructor (one that I've written).</p>
  
  <p>My program receive requests to create instances of an  objects with a parameter ID.
  I want to stop the constructor if the ID parameter contains a char that is not a digit.</p>
  
  <p>I cannot check the parameter before, since I'm not the one who calls the constructor.</p>