101     /**

   101     /**

   102      * The underlying map. Uses Boolean.TRUE as value for each

   102      * The underlying map. Uses Boolean.TRUE as value for each

   103      * element.  This field is declared final for the sake of thread

   103      * element.  This field is declared final for the sake of thread

   104      * safety, which entails some ugliness in clone().

   104      * safety, which entails some ugliness in clone().

   105      */

   105      */

   106     private final ConcurrentNavigableMap<E,Object> m;

   107     private final ConcurrentNavigableMap<E,Object> m;

   107 

   108 

   108     /**

   109     /**

   109      * Constructs a new, empty set that orders its elements according to

   110      * Constructs a new, empty set that orders its elements according to

   110      * their {@linkplain Comparable natural ordering}.

   111      * their {@linkplain Comparable natural ordering}.