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
  • 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
    • Exceptions
    • Assertions
    • Workshop: Throwing and Catching Exceptions
    • Summary
    • Q&A
    • Quiz
    • Questions
    • Activities
  • 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 18. Handling Errors in a Program

No subject in this book is less popular than the one you're about to tackle: errors.

Errors—the various bugs, blunders, typos, and other problems that stop a program from running successfully—are a natural part of the software development process. "Natural" is probably the kindest word that has ever been used to describe them—in my own Java programming, when I can't find the cause of an elusive error that keeps my program from working, I use words that would make a gangsta rapper blush.

Some errors are flagged by the compiler and prevent you from creating a class. Others are noted by the interpreter in response to a problem that keeps it from running successfully.

There are two kinds of problems you will encounter in Java:

• Exceptions— Events that signal an unusual circumstance has taken place as a program runs
• Errors— Events that signal the interpreter is having problems that may be unrelated to your program

During this hour, we'll explore exceptions as the following topics are discussed:

• How to use methods that cause exceptions
• How to respond to exceptions in your Java programs
• How to create methods that ignore an exception, leaving it for another class to handle
• How to create your own exceptions

You'll also learn about a new feature of version 1.4 that helps keep errors out of your programs: assertions.

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