Java archive
<file format, filename extension> (jar) A compressed archive file containing Java class files, filename extension: ".jar".
The Java Development Kit contains a tool called "jar" for creating .jar files, similar to the standard Unix tar command.
As well as archiving and compressing the Java class files, it also inserts a "manifest" file which can contain information about the class files, such as a digital signature.
Combining class files into a single archive file makes it possible to download them in a single HTTP transaction.
This, and the compression, speeds up execution of Java programs delivered via the Internet.
