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
    • Getting Your Programs to Listen
    • Setting Up Components to Be Heard
    • Handling User Events
    • Workshop: A Little Lotto Madness
    • Summary
    • Q&A
    • Quiz
    • Activities
  • 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

Setting Up Components to Be Heard

After you have implemented the interface needed for a particular component, you have to set that component to generate user events. A good example is the use of JButton objects as components. When you use a button in an interface, something has to happen in response to the click of the button.

The program that should respond to the button-click must implement the ActionListener interface. This interface listens for action events, such as a button-click or the press of the Enter key. To make a JButton object generate an event, use the addActionListener() method, as in the following:

JButton fireTorpedos = new JButton("Fire torpedos"); 
fireTorpedos.addActionListener(this); 

This code creates the fireTorpedos button and then calls the button's addActionListener() method. The this statement used as an argument to the addActionListener() method indicates that the current object will receive the user event and handle it as needed.

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