how to unpack visad.jar

What is the program to unpack visad.jar? thanks.
===================================
Dr Lin Feng

Nanyang Technological University
School of Applied Science
Blk N4, #2A-32
Nanyang Avenue
Singapore 639798

Phone: 7906184(Office), 7904828(Lab)
Fax:   7926559(Office), 7924117(Lab)
Email: asflin@xxxxxxxxxx
HTTP://www.ntu.edu.sg/home/asflin
===================================