Questions and Exercises: Annotations问题和练习：批注

Questions问题

1. What is wrong with the following interface?以下界面有什么问题？

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

2. Consider this implementation of the House interface, shown in Question 1.考虑到在1中所示的House接口的实现。

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

   If you compile this program, the compiler produces a warning because open was deprecated (in the interface).如果编译此程序，编译器将生成警告，因为open已弃用（在接口中）。What can you do to get rid of that warning?你能做些什么来摆脱这个警告？

3. Will the following code compile without error? Why or why not?下面的代码编译时不会出错吗？为什么？

   public @interface Meal { ... }
   
   @Meal("breakfast", mainDish="cereal")
   @Meal("lunch", mainDish="pizza")
   @Meal("dinner", mainDish="salad")
   public void evaluateDiet() { ... }

Exercises练习

1. Define an annotation type for an enhancement request with elements id, synopsis, engineer, and date.使用元素id、synopsis、engineer和date为增强请求定义批注类型。Specify the default value as unassigned for engineer and unknown for date.将默认值指定为工程师unknown和日期unknown。

Check your answers.检查你的答案。