description of the method concode_field_sep UserTracker instance concode_elem_sep UserDatabase usersDB concode_elem_sep HashMap<String,HashMap<String,LessonTracker>> storage concode_field_sep Collection<String> getAllUsers concode_elem_sep Collection getUsers concode_elem_sep LessonTracker getLessonTracker concode_elem_sep LessonTracker getLessonTracker concode_elem_sep void deleteUser concode_elem_sep void update concode_elem_sep int getCompleted concode_elem_sep String getStatus concode_elem_sep HashMap<String,LessonTracker> getUserMap
UserTracker function ( ) { if ( instance == null ) { instance = new UserTracker ( ) ; } return instance ; }