Vladimir Ozerov wrote:No, it should not. Beacause non-static methods can access static fields or methods, but not vice versa: static methods cannot access non-static fields or methods.
Generally that is true.
However, the problem here is the synchronization. The non-static, synchronized methods of different instances of this class can be executed in parallel. In this case, the static fields are not accessed from within these methods in a thread-safe way, despite the methods being declared synchronized.
So I'd say the answer to Tapio's question is that the generateMessage() should probably be declared static synchronized, if its purpose is to generate unique messages. The implementation as it was posted is flawed in this regard. However, I'd prefer to use AtomicInteger for that purpose.