Start of Tutorial > Start of Trail > Start of Lesson

Search Feedback Form

Implementing the Sleeper Interface

An interface defines a protocol of behavior. A class that implements an interface adheres to the protocol defined by that interface. To declare a class that implements an interface, include an implements clause in the class declaration. Your class can implement more than one interface (the Java platform supports multiple interface inheritance), so the implements keyword is followed by a comma-separated list of the interfaces implemented by the class.

---

By Convention:  The implements clause follows the extends clause, if it exists.

---

The GUIClock class implements the Sleeper interface, which contains a single method declaration for the wakeUp method. Thuse GUIClock must implement the wakeUp method:

public class GUIClock extends Applet implements Sleeper {
    . . .
    public void wakeUp() {
        // update the display
    }
}

Remember that when a class implements an interface, it is essentially signing a contract. The class must provide method implementations for all of the methods declared in the interface and its superinterfaces. Or, the class must be declared abstract. The method signature (the name and the number and type of arguments) for the method in the class must match the method signature as it appears in the interface.

Start of Tutorial > Start of Trail > Start of Lesson

Search Feedback Form