How to delete multiple columns in the same row?

[S. Zhou]

I try to delete multiple columns for the same row in HBase. I checked the API 
for the "Delete" class, method "deleteColumns", and have some confusion. 
Basically, I am not sure: if I should call "deleteColumns" on the same "Delete" 
object multiple times (to delete multiple columns), or create multiple "Delete" 
objects and each such object is for one column deletion.

Thanks
Senqiang