Add a method that returns an empty collection if a passed in collection is null

    public static <T> List<T> emptyIfNull(List<T> list) {
        return list == null ? Collections.<T>emptyList() : list;
    }

    public static <T> Set<T> emptyIfNull(Set<T> set) {
        return set == null ? Collections.<T>emptySet() : set;
    }

    public static <K,V> Map<K,V> emptyIfNull(Map<K,V> map) {
        return map == null ? Collections.<K,V>emptyMap() : map;
    }