1. Understanding and Creating Jar files in Java

2. Jar Files Jar files encompass a Zip format Can be digitally signed.
The JavaTM Archive (JAR) file format enables you to bundle multiple files into a single archive file.
Typically a JAR file will contain the class files and auxiliary resources associated with applets and applications
Jar files encompass a Zip format
Files are compressed to save space.
Can be digitally signed.
Programs can be run from Jar files without being un-archived.

3. Jar Files Use the Jar tool to create Jar files Syntax
Jar [options][manifest] destination input-file
c:\ Jar cf jarfile.jar *.class
This would “package” all the class files in the folder.
Jar cf jarfile.jar *.*
This would “package” all the files in the folder.

4. Jar Files Options c creates a new jar file
f the argument following this option specifies a Jar file to work with.
t lists the table of contents
x [file] extracts all the files
If [file] is named, it will extract only that file
m includes manifest information
M specifies that a manifest NOT be created
u Updates an existing Jar file by adding files or changing the manifest.

5. Jar Manifest Files Manifest files are text files. Include
Manifest-version: 1.1
Main-Class: {name of class file with main function}
(remember to have a blank line here)
File is named myManifest.mf
NOTE file must end with a blank line.

6. Jar File Usage Getting the contents of a jar Extracting files
jar tf myfile.jar
Extracting files
jar xf myfile.jar // extracts all the files
Jar xf myfile.jar my.class // extracts the my.class
Updating a jar
jar uf myfile.jar myclass.class
Building a jar
Jar cmf mymanifest.mf myfile.jar *.class
This would only include the class files
Jar cmf mymanifest.mf myfile.jar *.class *.java
This would include the java files and class files