(jar) A compressed archive file containing Javaclass files, filename extension: ".jar".The Java Development Kit contains a tool called "jar" for creating .jar files, similar to the standard Unixtar 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.(2001}-02-03)