This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
JAR files do have some stuff that has to do with versioning. I don't know how CAB file versioning works so I can't tell you if you can do the same things with JAR files. See the JAR File Specification for more information.