Well, it will depend on your database implementation but..
I believe 'read commited' usually means 'Show me only rows who's changes have been committed to the database'
So, if you try a read a row whilst a write is taking place, you will see the data prior to the write, until the row change is committed.
But really, you don't want
JDBC's semantics for this, you want the underlying db's implementation of how it works.