User Task Delegation / Reassign from Tasklist

Sir,

I would like to know more about, how can I delegate or reassign all my tasks to a different user with duration?
Currently my workflow custom app (JSF) is working fine and also able to assign to the respective user. When the user login to the Camunda and he could able to approve/reject.
But the user would like to reassign all his tasks to the the different person so that he could able to approve or reject. Could you please help us on this.

Is there any way user can do using Task List?? or ??

Thanks & Regards
Srini