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 digitalsignature. 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.