Answers to Questions and Exercises: Annotations

Questions

1. Question: What is wrong with the following interface:

   public interface House {
       @Deprecated
       public void open();
       public void openFrontDoor();
       public void openBackDoor();
   }
   

   Answer The documentation should reflect why open is deprecated and what to use instead. For example:

   public interface House { 
       /**
        * @deprecated use of open is discouraged, use
        * openFrontDoor or openBackDoor instead.
        */
       @Deprecated
       public void open(); 
       public void openFrontDoor();
       public void openBackDoor();
   }
   

2. Question: Consider this implementation of the House interface, shown in Question 1.

   public class MyHouse implements House {
       public void open() {}
       public void openFrontDoor() {}
       public void openBackDoor() {}
   }
   

   If you compile this program, the compiler complains that open has been deprecated (in the interface). What can you do to get rid of that warning?

   Answer: You can deprecate the implementation of open:

   public class MyHouse implements House { 
       //The documentation is inherited from the interface.
       @Deprecated
       public void open() {} 
       public void openFrontDoor() {}
       public void openBackDoor() {}
   }
   

   Alternatively, you can suppress the warning:

   public class MyHouse implements House { 
       @SuppressWarnings("deprecation")
       public void open() {} 
       public void openFrontDoor() {}
       public void openBackDoor() {}
   }