Java APIs

I've been trying to figure this out for awhile now, and I have not seen an example that will set me on the right track. Given the following code:

        public TreeSet<String> sort = new TreeSet<String>(CI_NE_Comparator);

        public static Comparator CI_NE_Comparator = new CaseInsensitiveNeverEqualsComparator();

        public static class CaseInsensitiveNeverEqualsComparator implements Comparator
	{
		public int compare(Object o1, Object o2)
		{
			String s1 = (String) o1;
			String s2 = (String) o2;
			int compare = s1.trim().toLowerCase().compareTo(s2.trim().toLowerCase());
			if (compare == 0)
			{
				return 1; // ensure like values are never deemed equal
			}
			return compare;
		}

	}

I'm getting a warning declaring the class variable sort:

Type safety: The expression of type Comparator needs unchecked conversion to conform to Comparator <? super String>

So just what is the proper method to make the Comparator conform to generics?

** Btw - if anyone knows of a better way to do that comparator, I'm all ears!