Java Applets

When the interaction between user and Web page exceeds the capabilities of HTML, experienced programmers may prefer to “roll their own” programs to handle the special needs not available in existing plug-ins. The Java programming language fills this need. Developed by Sun Microsystems, this language enables programmers to write small applications (applets) that download to the browser as separate files.

An applet runs as the user needs it and then is automatically discarded from memory when the user moves elsewhere in the Web. Animation, including animated text whose content can change over time, is a popular application of the Java applet in an HTML page. Because applets can also communicate with the Internet as they run (it is a very network-centric programming language), they are also used for real-time, data-streaming applications that display up-to-the-minute news, stock market, and sports data as this information comes across the wires. Standard HTML content can surround all of this activity as the Web page designer sees fit.

To play a Java applet, a browser company must license the technology from Sun and build it into its browser (or link up with a Java engine that is part of the operating system). Netscape was the first third-party browser supplier to license and produce a browser capable of running Java applets (Navigator 2 under Windows 95 and UNIX). Today, both Netscape Navigator and Microsoft Internet Explorer (IE) can load and run Java applets on almost every operating system platform supported by the browser.

Despite a flash of popularity in the early Java days, Java is used less and less for browser applets. It is quite popular, however, on the server, where it is used frequently to create small server application modules called servlets. On the client, Java applets suffer the same problem as some plug-ins: the delay required to download the file. Also, not every browser is equipped with the desired Java component, causing potential compatibility conflicts.