Let's say that we design a new Java class called Stuff that has 6 methods in total. Four of these methods will defined as synchronized. Two of the synchronized methods will modify a data structure called foo in the instantiated object. The other two synchronized methods will modify a data structure called bar.

We then create a new Stuff object. It is now concurrently (i.e., at the same time) accessed by 6 different threads. Each of the 6 threads calls a different one of the 6 methods (so all 6 methods are being invoked).

How many of the 6 threads will have to wait/block at this moment?