You get the same problem for strings. How do you know that you should lock "user_update" and not "update_user" for example? And how do you avoid name collision when client A wants to check for a lock that is used by client B for other purposes?

The solution to both cases is to define them as either static constants or use an Enum. Then you would not care if the end result is a string or a number.

At my work place we simply have a static class with lock names that we use.