SetFromMap(Map map) 
{
            if (!map.isEmpty())
                throw new IllegalArgumentException("Map is non-empty");
            m = map;
            s = map.keySet();
}

 public boolean add(E e) 
{
 return m.put(e, Boolean.TRUE) == null;
}

 public  void clear() 
{
        m.clear();
}

 public boolean contains(Object o) 
{
 return m.containsKey(o);
}

 public boolean containsAll(Collection c) 
{
return s.containsAll(c);
}

 public boolean equals(Object o) 
{
 return o == this || s.equals(o);
}

 public int hashCode() 
{
 return s.hashCode();
}

 public boolean isEmpty() 
{
 return m.isEmpty();
}

 public Iterator iterator() 
{
 return s.iterator();
}

 public boolean remove(Object o) 
{
 return m.remove(o) != null;
}

 public boolean removeAll(Collection c) 
{
return s.removeAll(c);
}

 public boolean retainAll(Collection c) 
{
return s.retainAll(c);
}

 public int size() 
{
 return m.size();
}

 public Object[] toArray() 
{
 return s.toArray();
}

 public T[] toArray(T[] a) 
{
 return s.toArray(a);
}

 public String toString() 
{
 return s.toString();
}