Hi,
> I am using drag and drop to display TIFF image. Is there another way to
> display TIFF files ? e.g., through java codes?
are you talking about uDig? JGrasstools has no UI, so I assume yes.
In that case you should place that question in the uDig mailinglist,
which can be found at the bottom of the site:
http://udig.github.io/
Andrea