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
    • for Loops
    • while Loops
    • do-while Loops
    • Exiting a Loop
    • Naming a Loop
    • Workshop: Teaching Your Computer a Lesson
    • Summary
    • Q&A
    • Quiz
    • Activities
  • 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

Hour 8. Repeating an Action with Loops

One of the more annoying punishments for schoolchildren is to make them write something over and over again on paper or a chalkboard.

On The Simpsons, in one of his frequent trips to the board, Bart Simpson had to write, "I am not certified to remove asbestos" dozens of times. This kind of punishment might work on children, but it definitely would fail to be punitive to a computer, which can repeat a task with ease.

Computer programs are ideally suited to do the same thing over and over again because of loops. A loop is a statement or set of statements that will be repeated in a program. Some loops take place a fixed number of times. Others take place indefinitely.

There are three loop statements in Java: for, do, and while. These statements are often interchangeable in a program because each can be made to work like the others. The choice to use a loop statement in a program often depends on personal preference, but it's beneficial to learn how all three work. You can frequently simplify a loop section of a program by choosing the right statement.

The following topics will be covered during this hour:

• Using the for loop
• Using the while loop
• Using the do-while loop
• Exiting a loop prematurely
• Naming a loop

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