The Java language supports the use of Java packages to manage the namespace of classes, but provides no mechanism for installing or managing packages. The Microsoft virtual machine (the version included with Internet Explorer 4.0 and with the Microsoft SDK for Java 3.2, or later) includes the Java Package Manager (JPM) to handle package installation and management. The primary function of JPM is to find classes when they are needed by the Microsoft virtual machine (Microsoft VM). When a class is needed, the JPM determines what package the class is in, and then refers to an internal database to determine where the package is stored. All the standard Java packages shipped with Microsoft® Internet Explorer 4.0 are installed in the Package Manager.
The following is a list of JPM features:
Version Control
Package version numbers are tracked, allowing Java programs and installers to intelligently update the system.
Application Namespaces
Java applications are installed in private namespaces, shielding their classes from name conflicts and use by other applications.
Improved Security
Instead of having to fully trust all installed classes, the Package Manager stores the allowed capabilities of each package as verified by Microsoft® Authenticode.
Ease Of Use
Java applications can install packages without having to alter the CLASSPATH environment variable and without requiring a restart.
Compatibility
The JPM will install ZIP and JAR archives as well as cabinet file archives.