public boolean add(Object object) 
{
        throw new UnsupportedOperationException();
}

 public boolean addAll(Collection coll) 
{
        throw new UnsupportedOperationException();
}

 public  void clear() 
{
        throw new UnsupportedOperationException();
}

 public static SortedSet decorate(SortedSet set) 
{
                                  
        if (set instanceof Unmodifiable) {
            return set;
        }
        return new UnmodifiableSortedSet(set);
}

Factory method to create an unmodifiable set.

 public SortedSet headSet(Object toElement) 
{
        SortedSet sub = getSortedSet().headSet(toElement);
        return new UnmodifiableSortedSet(sub);
}

 public Iterator iterator() 
{
        return UnmodifiableIterator.decorate(getCollection().iterator());
}

 public boolean remove(Object object) 
{
        throw new UnsupportedOperationException();
}

 public boolean removeAll(Collection coll) 
{
        throw new UnsupportedOperationException();
}

 public boolean retainAll(Collection coll) 
{
        throw new UnsupportedOperationException();
}

 public SortedSet subSet(Object fromElement,
    Object toElement) 
{
        SortedSet sub = getSortedSet().subSet(fromElement, toElement);
        return new UnmodifiableSortedSet(sub);
}

 public SortedSet tailSet(Object fromElement) 
{
        SortedSet sub = getSortedSet().tailSet(fromElement);
        return new UnmodifiableSortedSet(sub);
}