pure interface of interface java.util.SortedMap<A, B>

public interface SortedMap<A, B>
  implements Map<A, B>
{
    public abstract Comparator<A> comparator();
    public abstract SortedMap<A, B> subMap(A fromKey,
                                           A toKey);
    public abstract SortedMap<A, B> headMap(A toKey);
    public abstract SortedMap<A, B> tailMap(A fromKey);
    public abstract A firstKey();
    public abstract A lastKey();
}