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Chapter 2: Objects and Primitive Data Presentation slides for Java Software Solutions for AP* Computer Science by John Lewis, William Loftus, and Cara Cocking Java Software Solutions is published by Addison-Wesley Presentation slides are copyright 2002 by John Lewis, William Loftus, and Cara Cocking. All rights reserved. Instructors using the textbook may use and modify these slides for pedagogical purposes. *AP is a registered trademark of The College Entrance Examination Board which was not involved in the production of, and does not endorse, this product.
An object represents something with which we can interact in a program
An object provides a collection of services that we can tell it to perform for us
The services are defined by methods in a class that defines the object
A class represents a concept, and an object represents the embodiment of a class
A class can be used to create multiple objects
Objects and Classes Bank Account A class (the concept) John’s Bank Account Balance: $5,257 An object (the realization) Bill’s Bank Account Balance: $1,245,069 Mary’s Bank Account Balance: $16,833 Multiple objects from the same class
The classes of the Java standard class library are organized into packages
Some of the packages in the standard class library are:
Package java.lang java.applet java.awt javax.swing java.net java.util javax.xml.parsers Purpose General support Creating applets for the web Graphics and graphical user interfaces Additional graphics capabilities and components Network communication Utilities XML document processing