Similar code for [StackWrap4J][1]:

    List<Users> allUsers = new UsersList(
          new StackWrapper("api.stackapps.com"), 
          new UserQuery()
    );


You can then iterate through `allUsers` and see their `lastAccessDate`.  The currently released version will plow through the allowed calls per second, but v1.1 will properly throttle the requests.

[1]: http://stackapps.com/questions/818/stackwrap4j-java-wrapper