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
    • Storing Text in Strings
    • Displaying Strings in Programs
    • Using Special Characters in Strings
    • Pasting Strings Together
    • Using Other Variables with Strings
    • Advanced String Handling
    • Workshop: Presenting Credits
    • Summary
    • Q&A
    • Quiz
    • Activities
  • 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
  • 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

Using Other Variables with Strings

Although you can use the + operator to paste two strings together, as demonstrated in the preceding section, you will use it more often to link strings and variables. Take a look at the following:

int length = 121;
char rating = 'R';
System.out.println("Running time: " + length + " minutes");
System.out.println("Rated " + rating); 

This code will be displayed as the following:

Running time: 121 minutes
Rated R 

This example displays a unique facet about how the + operator works with strings. It can cause variables that are not strings to be treated just like strings when they are displayed. The variable length is an integer set to the value 121. It is displayed between the strings Running time: and minutes. The System.out.println() statement is being asked to display a string plus an integer, plus another string. This statement works because at least one part of the group is a string. The Java language offers this functionality to make displaying information easier.

One thing you might want to do with a string is paste something to it several times, as in the following example:

String searchKeywords = "";
searchKeywords = searchKeywords + "drama ";
searchKeywords = searchKeywords + "romance ";
searchKeywords = searchKeywords + "New Zealand"; 

This code would result in the searchKeywords variable being set to drama romance New Zealand. The first line creates the searchKeywords variable and sets it to be an empty string, because there's nothing between the double quotation marks. The second line sets the searchKeywords variable equal to its current string, plus the string drama added to the end. The next two lines add romance and New Zealand in the same way.

As you can see, when you are pasting more text at the end of a variable, the name of the variable has to be listed twice. Java offers a shortcut to simplify this process a bit: the += operator. The += operator combines the functions of the = and + operators. With strings, it is used to add something to the end of an existing string. The searchKeywords example can be shortened by using +=, as shown in the following code:

String searchKeywords = "";
searchKeywords += "drama ";
searchKeywords += "romance ";
searchKeywords += "New Zealand"; 

This code produces the same result: searchKeywords is set to drama romance New Zealand.

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