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Teach Yourself Java in 21 Days, Eighth Edition

Teach Yourself Java in 24 Hours, Eighth Edition

Teach Yourself C++ in 24 Hours

Hour 4: Understanding How Java Programs Work

Notes and Corrections

• At the end of this hour, the workshop is a guided tour of several Java applets. Each of these shows how a Java program on the Web can be modified with the use of the PARAM tag. Visit each of the following pages with a Web browser that supports Java:
  • The Frog applet
  • The Puzzle applet
  • The RandomText applet
  

Source Files

• Blanks.class
• Blanks.java
• BlanksApplet.class
• BlanksApplet.html
• BlanksApplet.java
• DisplayXY.class
• DisplayXY.html
• DisplayXY.java
• Root.class
• Root.java
• RootApplet.class
• RootApplet.html
• RootApplet.java

Reader Questions

• Question: The last question of chapter 4 is "why don't Java applets require the same kind of special access as gateway programs?" I don't understand what you mean by "gateway programs". I have googled that phrase and asked several people at work and we can't figure that out.
  Answer: A gateway program is one that employs the Common Gateway Interface (CGI), a standard that tells a web server how to call another program and receive information back in return.
  When you used this book's web site to send me e-mail, this server used CGI to call a Perl mailer script. The script then used CGI to provide the HTML to display my response: "Your e-mail has been sent. Thanks for contacting me!"

Activities

• Solution 1: Visit JARS, the Java Applet Ratings Service, and use the search term Headline to find applets that display news headlines.
• Solution 2: DisplayXY.java, DisplayXY.class, and DisplayXY.html.