Packaging an applet into a JAR file
An important use of the JAR utility is to optimize applet loading. In Java 1.0, people tended to try to cram all their code into a single applet class so the client would need only a single server hit to download the applet code. Not only did this result in messy, hard-to-read (and maintain) programs, but the .class file was still uncompressed so downloading wasn’t as fast as it could have been.
JAR files solve the problem by compressing all of your .class files into a single file that is downloaded by the browser. Now you can create the right design without worrying about how many .class files it will generate, and the user will get a much faster download time.
Consider TicTacToe.java. It looks like a single class, but in fact it contains five inner classes, so that’s six in all. Once you’ve compiled the program, you package it into a JAR file with the line:
jar cf TicTacToe.jar *.class
This assumes that the only .class files in the current directory are the ones from TicTacToe.java (otherwise, you’ll get extra baggage).
Now you can create an HTML page with the new archive tag to indicate the name of the JAR file. Here is the basic applet tag:
<head><title>TicTacToe Example Applet
</title></head>
<body>
<applet code=TicTacToe.class
archive=TicTacToe.jar
width=200 height=100>
</applet>
</body>
You’ll need to run this file through the HTMLconverter application that comes with the JDK in order to get it to work.
