GSON正确地序列化枚举，但将其反序列化为String

    HashSet<Skill> tmp = new HashSet<Skill>();
    tmp.add(Skill.WOODCUTTING);
    tmp.add(Skill.FIREMAKING);
    String j;
    System.out.println(j = new GsonBuilder().create().toJson(tmp));
    System.out.println(new GsonBuilder().create().fromJson(j, HashSet.class));
    for (Object e : new GsonBuilder().create().fromJson(j, HashSet.class)) {
        System.out.println(e.getClass());
        System.out.println(e.toString());
    }
    HashSet<Skill> tmp = new HashSet<Skill>();