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
  • Part VI: Creating Multimedia Programs
  • Hour 21. Using Fonts and Color
    • Using the Font Class
    • Using the Color Class
    • Other Ways to Choose Colors
    • Workshop: Displaying a Danger Message
    • Summary
    • Q&A
    • Quiz
    • Activities
  • 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

Other Ways to Choose Colors

To use a color not included in the 13 constant variables, you must specify the color's sRGB or HSB values. sRGB, which stands for Standard Red Green Blue, defines a color by the amount of red, green, and blue that is present in the color. Each value ranges from 0, which means there is none of that color, to 255, which means the maximum amount of that color is present. Most graphics editing and drawing programs will identify a color's sRGB values.

If you know a color's sRGB value, you can use it to create a Color object. For example, an sRGB value for dark red is 235 red, 50 green, and 50 blue, and an sRGB value for light orange is 230 red, 220 green, and 0 blue. The following is an example of a panel that displays light orange text on a dark red background:

import java.awt.*; 
import javax.swing.*; 

public class GoBucs extends JPanel { 
    Color lightOrange = new Color(230, 220, 0); 
    Color darkRed = new Color(235, 50, 50); 

    public void paintComponent(Graphics comp) { 
        Graphics2D comp2D = (Graphics2D)comp; 
        comp2D.setColor(darkRed); 
        comp2D.fillRect(0, 0, 200, 100); 
        comp2D.setColor(lightOrange); 
        comp2D.drawString("Go, Buccaneers!", 5, 50); 
    } 
} 

This example calls the fillRect() method of Graphics2D to draw a filled-in rectangle using the current color. You will learn more about this method on Hour 23.

Another way to select a color in a Java program is the HSB system, which stands for Hue Saturation Brightness. Each of these values is represented by a floating-point number that ranges from 0.0 to 1.0. The HSB system isn't as commonly supported in graphics software, so you won't be using it as often in your programs as you use sRGB values.

However, one thing HSB values are convenient for is changing a color's brightness without changing anything else about the color. You'll see an example of this use and an example of using HSB values to choose a color in this hour's workshop.

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