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Trail: Learning the Java Language
Lesson: Interfaces and Packages

## Questions and Exercises: Creating Interfaces

> ### Questions

> > 1. What methods would a class that implements the `java.util.Iterator` interface have to implement?

> > 2. What is wrong with the following interface?

> > >     public interface SomethingIsWrong {
> > >         public void aMethod(int aValue){
> > >             System.out.println("Hi Mom");
> > >         }
> > >     }

> > 3. Fix the interface in question 2.

> > 4. Is the following interface valid?

> > >     public interface Marker {
> > >     }

> ### Exercises

> > 1. Write a class that implements the `Iterator` interface found in the `java.util` package. The ordered data for this exercise is the 13 cards in a suit from a deck of cards. The first call to `next` returns `2`, the subsequent call returns the next highest card, `3`, and so on, up to `Ace`. Write a small `main` method to test your class.

> > 2. Suppose that you have written a time server, which periodically notifies its clients of the current date and time. Write an interface that the server could use to enforce a particular protocol on its clients.

> Check your answers.

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