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.
If you allow multiple threads to access our data class simultaneously (for read operations, using ReadWriteLock), there is one important thing to know: RandomAccessFile.length() is NOT thread safe. So if you use RandomAccessFile.length() (e.g. to make sure not to read beyond EOF), use it within a synchronized block with the RandomAccessFile object as mutex (like you would do with calls to seek/read methods).
I made some tests with multiple threads and had java.io.EOFExceptions thrown from RandomAccessFile's read methods and it took me a while to find out that unsynchronized calls to RandomAccessFile.length() was the reason.