By Herbert J. Bernstein

© Copyright 2003 Herbert J. Bernstein

Class Instance are the actual realization as objects of classes or abstract data types that are the templates for the objects.

• Class
• An abstract data type defining both the states and the actions (the variables and the methods -- components) that an object must have in order to be an instance of that class.
• An object that is an instance of a given class may have additional states and actions prescribed by the definitions of other classes of which it is also an instance.
• Some languages (e.g. java) permit a class to act in whole or in part as an instance of itself (static components)
• Instance Methods
• Methods defined in the class that will be instantiated in the class instance objects.
• In java accessed by object_name.method(arguments)
• Distinguished from class methods (static methods) accessed in java by class_name.method(arguments)
• Instance Variables
• Variables defined in the class that will be instantiated in the class instance objects.
• In java accessed by object_name.variable
• Shared by all the instance methods of the same object.
• Distinguished from class variables (static variables) accessed in java by class_name.variable. Class variables act as global common storage.