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The Java™ Tutorials
Trail: Learning the Java Language
Lesson: Annotations
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The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.
See Dev.java for updated tutorials taking advantage of the latest releases.
See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.
See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.

Questions and Exercises: Annotations

Questions

  1. What is wrong with the following interface?

    public interface House {
     @Deprecated
     void open();
     void openFrontDoor();
     void openBackDoor();
    }
    
  2. 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 produces a warning because open was deprecated (in the interface). What can you do to get rid of that warning?

  3. Will the following code compile without error? Why or why not?

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

Exercises

  1. Define an annotation type for an enhancement request with elements id, synopsis, engineer, and date. Specify the default value as unassigned for engineer and unknown for date.

Check your answers.

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