What Is JAR (Java ARchive) File Format?

JAR (Java ARchive) is a platform-independent file format that aggregates many files into one file.

Originally, JAR file format is designed to bundle multiple Java applets and their requisite components (.class files, images and sounds) into a single file, which can be downloaded to a browser in a single HTTP transaction. This is 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.

Today, JAR becomes the standard package file format to distribute Java application software or Java libraries.

Main features of JAR file format:

• JAR files can be identified by MIME type of "application/java-archive".
• JAR files can also be identified by the.jar file extension.
• JAR files can be compressed using the ZIP specification.
• JAR files can be indexed to improve class loading speed.
• JAR files can support a manifest file containing name-value pairs to provide package configurations.
• A JAR can be configured as executable.
• A JAR can be configured as sealed,
• The manifest file can support many other features.

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