This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
It will INSERT or UPDATE depending on the value of the objects identifier (PK if you will). If your transient object has an identifier value, then update() is called, if it doesn't save() is called (which generates an identifier). So your new object should be inserted, unless you have already assigned an identifier which isn't in the DB, in which case an update statement will be called on a record that doesn't yet exist - which won't work of course. Show us your code if you are still confused.