Now sony has started rolling out much awaited Android Jelly bean update for Sony Xperia J (ST26i) Model.Sony Xperia J is the third of its kind to get updated to Android Jelly bean version 4.1.2 ( Build number 11.2.A.0.21 ).
Here is a screenshot of jelly bean updated updated Sony Xperia J.
As you can see the Jelly bean provides a power saver option which enables your device to cutoff data usage,Wifi and other powers consuming features when the phone is ideal.
How to Update ?
If you are a Windows user then use Sony PC companion (PCC) ,Mac users can use Sony Bridge for Mac.
Just connect your phone to your PC or Mac and start the PCC or Mac bridge and you will get a option to upgrade.