“Acquiring the lock associated with an object does not prevent other threads from accessing that object—the only thing that acquiring a lock prevents any other thread from doing is acquiring that same lock. The fact that every object has a built-in lock is just a convenience so that you needn't explicitly create lock objects. [9] It is up to you to construct locking protocols or synchronization policies that let you access shared state safely, and to use them consistently throughout your program. [9]”