About .JAR File Format
To do word count in JAR archives, let’s get to know a little more about this format.
A JAR (Java ARchive) file is mostly used to combine many Java class files and their metadata and resources (text, images, etc.) into one file for easy distribution.
JAR files may include a special manifest file that describes how to use the file. This increases security and can allow the Jar file to be executed directly.
JAR files use the file extension “.jar”. A JAR file contains one or more files that are compressed or stored. it can be opened with the jar command line utility: “jar -xf foo.jar”.
Since it is based on the ZIP format, many common software utilities can create, modify or open XPI files, notably 7-Zip, WinZip and WinRar.
Link:
WinZip Home Page
7-Zip Home Page
WinRAR Home Page