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Questions and Exercises: Creating and Using Interfaces

Questions

1. What methods would a class that implements the java.lang.CharSequence 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 CharSequence interface found in the java.lang package. Select one of the paragraphs from this book to use as the data. Write a small main method to test your class; make sure to call all four methods.

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

Check your answers.

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