How to start java Activity BPMN2.0 development with an easier and efficient way? Need for discussion or video tutorial.

IBM BPM (formerly Lombardi) is easy and efficient.

You can try for free at http://goo.gl/SEUERs

There are free (You Tube)  video tutorials at the above link mentioned.

You can also google for more tutorials. There is lots of material on IBM BPM on the web.