A subclass is a class that inherits properties and methods from another class, called the superclass. The extends
clause of the class statement lets you specify a class's superclass.
classsubClass
extendssuperClass
{ // Class properties, methods. }
The subclass inherits all the properties and methods of the superclass, including private properties and methods (see "Static, public, and private members" on page 140). A class can only inherit from a single class. A subclass can only inherit from a single superclass. Multiple inheritance is not allowed.
Classes you create can extend any of the built-in ActionScript classes like MovieClip, Button, or XML.