code: public void dropKeyspace(DBConn dbConn, String keyspace) {
          m_logger.info("Deleting Keyspace '{}'", keyspace);
          try {
              dbConn.getClientSession().system_drop_keyspace(keyspace);
              waitForSchemaPropagation(dbConn);
          } catch (Exception ex) {
              String errMsg = "Failed to delete Keyspace '" + keyspace + "'"; 
              m_logger.error(errMsg, ex);
              throw new RuntimeException(errMsg, ex);
          }
      }
docs: Delete the keyspace with the given name. This method can use any DB connection.
  
  @param dbConn    Database connection to use.
  @param keyspace  Name of keyspace to drop.