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
  • Hour 19. Creating a Threaded Program
  • Hour 20. Reading and Writing Files
    • Streams
    • Writing Data to a Stream
    • Workshop: Writing Bytes to an MP3 File
    • Summary
    • Q&A
    • Quiz
    • Questions
    • Activities
  • 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 20. Reading and Writing Files

There are numerous ways to represent data on a computer. You have already worked with one by creating objects—an object includes data in the form of variables and references to objects. It also includes methods that use the data to accomplish tasks.

To work with other kinds of data, such as files on your hard drive and documents on a Web server, you can use the classes of the java.io package. The "IO" part of its name stands for "input/output" and the classes are used to access a source of data, such as a hard drive, CD-ROM, or the computer's memory.

You can bring data into a program and send data out by using a communications system called streams, or objects that take information from one place to another.

During this hour, you will work with streams to do each of the following:

• Read bytes from a file into a program
• Create a new file on your computer
• Save an array of bytes to a file
• Make changes to the data stored in a file

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