| attribute name | possible values | meaning | notes |
|---|---|---|---|
| CODEBASE | URL | the base URL of the applet; this typically refers to the directory or folder containing the code of the applet | default is the URL of the document |
| CODE | string | class file, i.e. the name of the file that contains the compiled Applet subclass of the applet | obligatory; interpreted as relative to the base specified by the CODEBASE attribute; cannot be absolute |
| ALT | string | a textual description, to be displayed in place of applet | the contents of the element can be used for the same purpose, with more flexibility |
| NAME | string | a name for the applet instance | such names make it possible for applets in the same document to find (and communicate with) each other. |
| WIDTH | integer | suggested width, in pixels, not counting any windows or dialogs which the applet brings up | obligatory |
| HEIGHT | integer | suggested height, in pixels, not counting any windows or dialogs which the applet brings up | obligatory |
| ALIGN | TOP, MIDDLE, BOTTOM, LEFT, RIGHT | positioning of the applet display area | similar to ALIGN attribute of IMG |
| HSPACE | integer | suggested horizontal gutter (width of white space to the immediate left and right of the applet display area), in pixels | cf. to HSPACE attribute of IMG |
| VSPACE | integer | suggested vertical gutter (height of white space above and below the applet display area), in pixels | cf. to VSPACE attribute of IMG |
The exact meaning and intended use of text elements in the contents is somewhat obscure. The following is the wording of the HTML 3.2 Reference Specification:
Following the PARAM elements, the content of APPLET elements should be used to provide an alternative to the applet for user agents that don't support Java. - - Java-compatible browsers ignore this extra HTML code. You can use it to show a snapshot of the applet running, with text explaining what the applet does. Other possibilities for this area are a link to a page that is more useful for the Java-ignorant browser, or text that taunts the user for not having a Java-compatible browser.Notice that text elements in the contents and ALT attribute in the start tag are two ways of having something displayed in place of the applet. There are two differences: the value of ALT is a plain string, whereas the elements may contain text markup; and an ALT attribute has no effect if the browser does not know an APPLET element at all, whereas such a browser probably processes the text elements in the contents - it simply ignores the APPLET (and PARAM) start and end tags.
A simple example: an applet which draws animated bubbles.
<APPLET CODEBASE="http://java.sun.com/applets/other/Bubbles/classes" CODE="Bubbles.class" WIDTH=500 HEIGHT=500 ALIGN=MIDDLE> <P><IMG SRC="bubbles.gif" ALT="[GIF image (2k)]"><BR> An extract from a snapshot of <CITE>Bubbles</CITE> animation by <A HREF="http://java.sun.com/">java.sun.com</A>.</P> </APPLET>A more complicated example, using parameter passing (PARAM element):
<APPLET CODE="AudioItem" WIDTH=15 HEIGHT=15 ALIGN=TOP> <PARAM NAME=snd VALUE="Hello.au|Welcome.au"> <STRONG>Welcome!</STRONG> </APPLET>
An example of typical (?) use of Java applets for "decorative" purposes (which many people find annoying):
<APPLET CODEBASE="applets/NervousText"
CODE="NervousText.class"
WIDTH=300
HEIGHT=50>
<PARAM NAME=TEXT VALUE="Java is Cool!">
<IMG SRC="sorry.gif" ALT="This looks better with Java support">
</APPLET>
Our final example, as well as the first one, uses Java demo code from java.sun.com. It runs an applet for a nice game. Of course, the essential thing is the applet itself. The HTML constructs needed are simple and similar to the ones above. However, here the alternative texts just inform the user about Java being not in use. In cases like this, where the applet is essential, such notes might be the best you can do, although you might consider providing a snapshot for illustration (as in the first example) to help the reader to decide whether he really wants to see the applet in action.
<H3>Multilingual Word Match Game</H3> <P>This demonstration uses a Java applet (from <A HREF="http://java.sun.com/">java.sun.com</A>), so you need Java enabled on your browser to see it.</P> <P>First select a language on the left. The match words with pictures, clicking first on a picture, then on a word. Click on "score" to see how well you did.</P> <APPLET CODEBASE="." CODE="WordMatch.class" WIDTH=500 HEIGHT=350 ALT="(Your browser recognizes the APPLET element but does not run the applet.)"> <EM>Your browser either has no Java support at all or it has Java support disabled.</EM> </APPLET>
In HTML 4.0, the APPLET element is deprecated in favor of the new OBJECT element. However, the implementation of OBJECT is broken in many popular browsers.
Java is an object-oriented programming language (somewhat similar to C++) developed by Sun. A Java applet is a Java program which is executed by an interpreter invoked by (some) Web browsers upon encountering an APPLET element. Java applets can be used for animations, games, etc.
Even if a browser supports Java, the support can be disabled by system administration or by individual users, and people often do this because they think Java has too many security risks. Therefore, if you use Java applets, try to design your documents so that they work (although perhaps unimpressively) with Java disabled, too.
There is a very large number of Java applet examples on the Web. For some collections, see FREE Java and JavaScript at TheFreeSite.com. (But make sure you understand the difference between Java and JavaScript!)