B&S & Denny's: Design decisions (locking stuff really)

[Mickey Mulligan]

Hey,
I've seen how logical locking was implemented in Denny's DVD's, the project that came with the SCJD book. I'm looking to do something similar for my assignment (Bodgitt & Scarper), so I'll have a "LockingManager" class to handle locking and unlocking records. At the moment I've got (pseudocode):

Class Data implements DBAccess {
 
    databaseFileAccessor // Handles the file I/O stuff
    lockingManager // Handles logical locking stuff
 
    public long lockRecord(long recNo) throws RecordNotFoundException {
        if(!databaseFileAccessor.contains(recNo)) {
            throw RecordNotFoundException
        }
        // Thread can slice in here and screw stuff up
        return lockingManager.lock(recNo)
    }
}

I presume using a synchronized block to sort out the problem with threads slicing in is a good idea? Are there any other designs I should look at perhaps? I like the idea of keeping the locking seperate from File I/O so I want to keep it that way. But not if I'm going to lose marks for overuse of 'synchronized'!