When JFreeChart (1.0.8a) is used with the Oracle jdbc driver > V9 the method JDBCXYDataset.executeQuery will produce a ClassCastException at line 348.
The reason for this exception is the strange behavior of the oracle jdbc driver. If you call the method ResultSet.getObject on a TIMESTAMP column you will get a Object of class oracle.sql.TIMESTAMP, but oracle.sql.TIMESTAMP is NOT based on java.util.Date.
Bugfix