The return of the executeUpdate method indicates the number of records affected by the SQL statement. The setting of auto-commit for the Connection object determines whether each statement is committed automatically or whether an explicit commit or rollback must be done. If auto-commit is on, then each statement executed with executeUpdate method will be committed immediately. If auto-commit is off, a commit or rollback will be done only when a commit or rollback method of the Connection object is called. By default, new connections start with auto-commit on.
Different drivers handle locking, transaction isolation, and concurrency differently.
The driver's documentation will need to be consulted to determine how the driver behaves, and how compatible it will be with other applications that are accessing the database. It is important to have a pure JAVA driver when you need to use the driver in applets, since the driver must be downloaded to the client, just as the applet is. Actually, if all of the code that makes up a driver is not pure JAVA, it still may be possible to use the driver in an applet. Typically, drivers that use this approach use a network connection to access non-JAVA code on machines other than the client. The 1-tier method is used for JAVA applications that execute on the same machine the database resides on.