A huge mistake, I've seen a lot of code where clearly the author thought that just adding "synchronized" would have solved any concurrency issue. And no one even talks about how synchronized is implemented, basically a monitor on the object.
The point of view is usually also wrong, they focus on the method call flow while they should think about protecting access to shared data.
The point of view is usually also wrong, they focus on the method call flow while they should think about protecting access to shared data.