Hi Ashok Kuppuswamy,
Why do you need to do that? I think after you get a list of task that the user assigned as potential owner, all the task in your list is claimable by the user.
If you want to claim the task, just use the taskClient function to claim the task.
Basically what will happen is the Human Task Service will check again if that Task is claimable by the user by using its UserGroupCallback component, calling getGroupsForUser. If the user still able to claim the task, then the task will be claimed, if not, it will return an exception saying that the user does not have right to do that action (claim task).
Regards,
Thomas Setiabudi