How long it will take to insert 20 million rows to teradata table from java using jdbc drivers TYPE=FASTLOADCSV - response (1) by Kawish_Siddiqui

I don't think there is an absolute answer of this, you might need to look at some bench marking results for this but still it will be highly dependent upon I/O and network/communication capacity. 
http://developer.teradata.com/connectivity/articles/speed-up-your-jdbcodbc-applications might help in this.