Extracting .jar file with command line
From the docs:
To extract the files from a jar file, use
x, as in:C:\Java> jar xf myFile.jarTo extract only certain files from a jar file, supply their filenames:
C:\Java> jar xf myFile.jar foo bar
The folder where jar is probably isn't C:\Java for you, on my Windows partition it's:
C:\Program Files (x86)\Java\jdk[some_version_here]\binUnless the location of jar is in your path environment variable, you'll have to specify the full path/run the program from inside the folder.
EDIT: Here's another article, specifically focussed on extracting JARs: http://docs.oracle.com/javase/tutorial/deployment/jar/unpack.html