Implementing an Interface

Purpose:

To create a class that accepts the responsibilities declared in one or more interfaces.

Mechanics:

<modifiers> class <class name> implements <interface list> {
/* Instance variables declared and methods defined here */
}

Example:

public class myClass implements myInterface {
/* Instance variables declared and methods defined here */
}

Usage:

  • <modifiers> is an optional space-separated list of valid class modifiers.
  • <class name> is any valid identifier unique to the current scope.
  • <interface list> is a comma-separated list of interfaces which the class should implement. It is expected that a class which implements an interface will provide a definition for every method declared in that interface. If it does not, then the class must be declared abstract. <class name> has direct access to all class constants defined in the interfaces it implements.
  • An interface in <interface list> may inherit from one or more other interfaces. In this case, <class name> must provide a definition for the methods declared in the interface and all of its superinterfaces, or be declared abstract. Likewise, <class name> has direct access to all class constants defined in the superinterfaces.
  • A class that implements interfaces can also inherit from a superclass. The superclass must be extended before the interfaces are implemented:

    <modifiers> class <class name> extends <superclass name> implements <interface list> {
    /* Instance variables declared and methods defined */
    }

    public class myClass extends superClass implements myInterface {
    /* Instance variables declared and methods defined */
    }
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