@kanwar singh
user is a reserved word in hive. You need to use escape characters for it. They are the back ticks, e.g. `user`. Since you are passing the statement as a string, you may have to escape the back-tick ` as well using a back-slash, \`.
Additionally, commands issued in hive require a semi-colon at the end.
To test the above theory just try to drop a table that does not have a reserved keyword in hive, e.g. MyTable.
If this helps, please vote/accept answer.