I assume you mean a dog when adding many rows to the table. Try this: (sorry I don't have my code example handy) Instead of adding rows one at a time to the JTable using new Vectors, add new String to the underlying data model and then notify the JTable that its data has changed. MUCH faster!
I don't think it's the JTable itself but the default table model. Try making your own model. As a test, a couple months ago, I wrote a table model that had 100,000 rows and the JTable didn't slow down at all.