What is the main differences between a Lock and a synchronized block?

      A synchronized block makes no guarantees about the sequence in which threads waiting to entering it are granted access.

    You cannot pass any parameters to the entry of a synchronized block. Thus, having a timeout trying to get access to a synchronized block is not possible.

    The synchronized block must be fully contained within a single method. A Lock can have it's calls to lock() and unlock() in separate methods.