Statement.executeBatch() always returns an array of value -2

The elements in the array returned by the method executeBatch may be one of the following:

1. A number greater than or equal to zero -- indicates that the command was processed successfully and is an update count giving the number of rows in the database that were affected by the command's execution
2. A value of -2 -- indicates that the command was processed successfully but that the number of rows affected is unknown
   If one of the commands in a batch update fails to execute properly, this method throws a BatchUpdateException, and a JDBC driver may or may not continue to process the remaining commands in the batch. However, the driver's behavior must be consistent with a particular DBMS, either always continuing to process commands or never continuing to process commands. If the driver continues processing after a failure, the array returned by the method BatchUpdateException.getUpdateCounts will contain as many elements as there are commands in the batch, and at least one of the elements will be the following:
3. A value of -3 -- indicates that the command failed to execute successfully and occurs only if a driver continues to process commands after a command fails

reference : executeBatch