JDK 1.2 supports extensions, which are packages of Java classes (and
any associated native code) that application developers can use to
extend the functionality of the core platform. The extension mechanism
allows the Java Virtual Machine to use the extension classes in much
the same way as the Java VM uses the system classes. The extension
mechanism also provides a way to retrieve extensions from URLs when
they are not available as part of the JDK or the Java Runtime
Environment (JRE).
Extensions are packaged as JAR files and are installed in the
/lib/ext
directory of the JDK or the JRE. When installed
in the /lib/ext
directory, extensions can be used by applets and applications without
being explicitly included in the class path.