Sams Teach Yourself Java 2 in 24 Hours

By Rogers Cadenhead

• Table of Contents
  • Copyright
  • About the Author
  • About the Technical Editor
  • Acknowledgments
  • We Want to Hear from You!
  • Reader Services
  • Introduction
  • Hour 1. Becoming a Programmer
  • Hour 2. Writing Your First Program
  • Hour 3. Vacationing in Java
  • Hour 4. Understanding How Java Programs Work
  • Part II: Learning the Basics of Programming
  • Hour 5. Storing and Changing Information in a Program
  • Hour 6. Using Strings to Communicate
  • Hour 7. Using Conditional Tests to Make Decisions
  • Hour 8. Repeating an Action with Loops
  • Part III: Working with Information in New Ways
  • Hour 9. Storing Information with Arrays
  • Hour 10. Creating Your First Object
  • Hour 11. Describing What Your Object Is Like
  • Hour 12. Making the Most of Existing Objects
    • The Power of Inheritance
    • Establishing Inheritance
    • Working with Existing Objects
    • Workshop: Creating a Subclass
    • Summary
    • Q&A
    • Quiz
    • Activities
  • Part IV: Programming a Graphical User Interface
  • Hour 13. Building a Simple User Interface
  • Hour 14. Laying Out a User Interface
  • Hour 15. Responding to User Input
  • Hour 16. Building a Complex User Interface
  • Part V: Creating Multimedia Programs
  • Hour 17. Creating Interactive Web Programs
  • Hour 18. Handling Errors in a Program
  • Hour 19. Creating a Threaded Program
  • Hour 20. Reading and Writing Files
  • Part VI: Creating Multimedia Programs
  • Hour 21. Using Fonts and Color
  • Hour 22. Playing Sound Files
  • Hour 23. Working with Graphics
  • Hour 24. Creating Animation
  • Part VII: Appendixes
  • Appendix A. Tackling New Features of Java 2 Version 1.4
  • Appendix B. Using the Java 2 Software Development Kit
  • Appendix C. Programming with the Java 2 Software Development Kit
  • Appendix D. Using Sun ONE Studio
  • Appendix E. Where to Go from Here: Java Resources
  • Appendix F. This Book's Web Site

Q&A

1. Can a class have more than one superclass so that it inherits additional methods and behavior?

   It is possible with some object-oriented programming languages, but not Java. One of the goals when Java was developed was to provide a simpler language than an object-oriented language such as C++, and limiting inheritance to a single superclass was one way to achieve this. You can use a special type of class called an interface to inherit behavior that isn't received from superclasses.

2. Most Java programs created up to this point have not used extends to inherit from a superclass. Does this mean they exist outside of the class hierarchy?

   All classes you create in Java are part of the hierarchy because the default superclass for the programs you write is Object when the extends keyword is not used. The equals() and toString() methods of all classes are part of the behavior that automatically is inherited from Object.

3. Are JavaBeans anything like ActiveX controls?

   JavaBeans and Microsoft ActiveX are different answers to the question, "What's the best way to create reusable software components?" ActiveX is a simplified adaptation of the Component Object Model, a complex standard for software component programming that can be implemented in many different programming languages. ActiveX controls can be developed with several different languages, including Java. One of the things a JavaBeans programmer learns is how to turn a Bean into an ActiveX control.

4. When is the full name of a class, such as java.applet.Applet , needed in an extends clause instead of a shorter name such as Applet ?

   You must use the full name whenever you don't use an import javax.swing.JApplet; or import.javax.swing.*; statement at the beginning of your program. The import statement is used solely to make it easier to refer to class names in programs. Each class of objects in Java has a full name that identifies the group of classes to which it belongs. For instance, the Math class is part of the java.lang group of classes. A group of classes is also called a package.

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