public class CollectionUtils {
    public static <T extends Comparable<? super T>> Comparator<T> comparableComparator() {
        return new Comparator<T>() {
            public int compare(T o1, T o2) {
                return o1.compareTo(o2);
            }
        };
    }

    public static <T> Comparator<T> reverseComparator(
            final Comparator<T> c) {
        return new Comparator<T>() {
            public int compare(T o1, T o2) {
                return -c.compare(o1, o2);
            }
        };
    }
                                                 
    public static <T extends Comparable<? super T>> Comparator<T> reverseComparableComparator() {
        return CollectionUtils.reverseComparator(CollectionUtils.<T>comparableComparator());
    }

    private static Object foo() {
        return new TreeMap<Integer, Object>(reverseComparableComparator());        // IDEA doesn't highlight an error, but javac does: incompatible types; inferred type argument(s) java.lang.Comparable<? super T> do not conform to bounds of type variable(s) T
    }