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.
The lock is on the instance of the Friend object and not on the instance of Friend.class object. There are 2 friend objects. Locking on one does not prevent the other instance from executing the method.