package api;

 // BEGIN: forjoe.InterfaceThatJustJoeCanImplement

 public abstract class InterfaceThatJustJoeCanImplement {

     protected InterfaceThatJustJoeCanImplement() {

         if (!"impl.joe.JoesImpl".equals(getClass().getName())) {

             throw new IllegalStateException(

                 "Sorry, you are not allowed to implement this class"

             );

         }

     }

     public abstract void everyoneCallThisJoeWillHandleTheRequest();

 }

 // END: forjoe.InterfaceThatJustJoeCanImplement