You can also use disk utility and make a dmg of your whole partition and store it on an external drive, which you can restore back onto your drive using an SL disk or Lion/Mountain Lion USB, but you will have to install iboot again.
I also prefer to use Apple's Disk Utility prior to installing any risky updates, but I choose to:
1) make an actual clone ("Restore") to an extra drive (not just a dmg***); depending on the size of your OS-apps-data this usually takes hours or even overnight, but worth it as a precautionary step.
2) I start up using a Unibeast USB thumb drive, press F12 after power-on on my Gigabyte mobo, enter the drive-select menu, then I boot from the freshly cloned drive (usually works without iBoot re-install)
3) Now that I am booted from the clone, I view this as a safe haven to run updates and fixes.
4) If I'm successful, I then boot from my main drive and run the same updates there. // Done. //
5) If things get screwed up, the clone I booted from is dispensable. I can reformat it and re-clone, then leverage try again using what I learned from my mistakes.
btw, despite the outline above of what I do when risking and testing new patches, I am surprised that a Java update could cause as much havoc as some are discovering. I normally do not have concerns about a simple Java update fouling up the OS. New Java might be incompatible with some types of applications (Oracle e.g.), but it should not brick a Mac or CustoMac.
To those who suffered post-Java problems: are you sure that *only* the Java update ran? Or did the App Store - Sofware Update deploy any other seemingly innocuous changes?
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***Note: since dmg's and Time Machine backups are not of themselves bootable, I use them to a lesser degree
