When is it OK to use exception handling for business logic?

Question

I think it is accepted that as a general rule in Java (and perhaps any language with exception handling) one should try to avoid using exception handling to actually handle

Answer 1

If you are dealing with an error condition which is actually a part of the business logic, it is OK to use Exceptions. For example:

try{
   // register new user
   if(getUser(name) != null)
      throw new MyAppException("Such user already exists");
   //other registration steps......
}catch(MyAppException ex){
   sendMessage(ex.getMessage());
}