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
    • First Stop: Sun Microsystems
    • Going to School with Java
    • Lunch in JavaWorld
    • Taking in a Ballgame at ESPN.com
    • Getting Down to Business
    • Stopping by Gamelan to Ask Directions
    • Workshop: Putting Java on Your Desktop
    • Summary
    • Q&A
    • Quiz
    • Activities
  • 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
  • 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

Getting Down to Business

At this point in your travels, you might be getting the impression that Java is primarily of use to baseball fans and those who have body parts to show the world. Although those two subject areas are enough to keep most of us entertained for days, the next stop on our trip shows an example of Java getting down to business.

Direct your Web browser to http://www.uralbeacon.co.uk/zoomchart. This example is a financial charting tool presented as a Java program. Historical price and average data is displayed, and users can drag the mouse over an area on a chart to define a new portion of the data to chart, as shown in Figure 3.5.

Figure 3.5 A Java program from Ural Beacon that is used to analyze financial data such as stock market prices.

Unlike other stock analysis programs that require the installation of software on the computers of each employee who needs access, the use of Java enables Ural Beacon to make the program available to anyone with a Web browser—all the employees would have to do is access the company's Web site.

A program such as Ural Beacon's charting applet can be thought of in several different ways. One way is to think of a program as an object—something that exists in the world, takes up space, and has certain things it can do. Java, like the C++ language, uses object-oriented programming, as you will see during Hour 10, "Creating Your First Object." Object-oriented programming (OOP) is a way to design computer programs. A program is thought of as a group of objects. Each object handles a specific task and knows how to speak to other objects. For example, a word processing program could be set up as the following group of objects:

• A document object, which is the area where you type in text
• A spell-checking object, which can look over the document object to find any possible spelling errors
• A printer object, which handles the printing of the document
• A menu object, a mouse object, and many others

The word processing software is a collection of all the objects necessary to get work done.

OOP is a powerful way to create programs, and it makes the programs you write more useful. Consider word processing software. If the programmer wants to use the spell-checking capabilities of that program with some other software, the spell-checking object is ready for use with the new program. No changes need to be made.

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