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JAR (Java Archive) is a platform-independent file format that aggregates many files into one. Multiple Java applets and their requisite components (.class files, images and sounds) can be bundled in a JAR file and subsequently downloaded to a browser in a single HTTP transaction, greatly improving the download speed. The JAR format also supports compression, which reduces the file size, further improving the download time. In addition, the applet author can digitally sign individual entries in a JAR file to authenticate their origin. It is fully extensible.

Overview and Specification

• Overview - An overview of JAR Files
• Specification - The JAR File Specification

API Specification

• java.util.jar Package
• java.net.JarURLConnection

Tutorials and Programmer's Guides

• A tutorial introduction to JAR files.

Enhancements

• Enhancements in JDK^TM 6 - An annotated list of changes between the 5.0 and 6.0 releases to APIs, the jar command, and the jar/zip implementation.

JAR Tools

• JAR tool reference page for Solaris
• JAR tool reference page for Windows

More Information

• Extension Mechanism Architecture - The mechanism for extending the Java platform uses the JAR file format to package extension classes. Manifest attributes are available to support the extension mechanism and related features such as package sealing and package versioning.