Sending Parameters from a Web Page

Now that you have had some experience writing computer programs, you might be feeling one of the strongest emotions of the programmer: compiler angst. Even though it takes no more than 15 seconds to compile most programs, that time can seem interminable when you're debugging a program. Write, save, compile, Aargh—an error! Write, save, compile, Aargh! Write, save, compile, Aargh!… As this vicious cycle repeats itself, it's easy to become world-weary as a program is compiled and recompiled. One of the driving forces behind parameter use in Java applets is the fear and loathing of compilation. Parameters enable you to change elements of an applet without editing or recompiling anything. They also make the program more useful. Parameters are stored as part of the web page that contains an applet. They are created using the HTML tag param and its two attributes: name and value. You can have more than one param tag with an applet, but all of them must be between the opening <applet> tag and the closing </applet> tag, which also support parameters). The following is an applet tag that includes several parameters:

<applet code="ScrollingHeadline.class" >
<param value="Dewey defeats Truman">
<param value="Stix nix hix pix">
<param value="Man bites dog">
</applet>

This example could be used to send news headlines to an applet that scrolls them across the screen. Because news changes all the time, the only way to create a program of this kind is with parameters. You use the name attribute to give the parameter a name. This attribute is comparable to giving a variable a name. The value attribute gives the named parameter a value.