枚举工具类

@Getter
@AllArgsConstructor
public enum GenderEnum {
               /**
	 * 性别枚举
	 */
	FEMALE("男"),
	MALE("女"),
	UNKNOWN("未知");

	private final String desc;

}

//                                            获取desc          通过ordinal 值为0
String desc = EnumUtil.getFieldBy(GenderEnum::getDesc, GenderEnum::ordinal, 0);
Assert.assertEquals("男", desc);

GenderEnum genderEnum = EnumUtil.getBy(GenderEnum::ordinal, RandomUtil.randomInt(0, 3));
if (genderEnum == null) {
	return;
}
switch (genderEnum) {
	case FEMALE:
	Console.log("这是一位帅帅的小哥哥");
		break;
	case MALE:
		Console.log("这是一位美美的小姐姐");
		break;
	case UNKNOWN:
		Console.log("这位更是重量级，Ta不愿意透露性别");
		break;
	default:
		break;
}

// Add test like a foreigner
Map<Integer, String> adjectivesMap = MapUtil.<Integer, String>builder()
		.put(0, "lovely")
		.put(1, "friendly")
		.put(2, "happily")
		.build();

Map<Integer, String> resultMap = MapUtil.change(adjectivesMap, (k, v) -> v + " " + PeopleEnum.values()[k].name().toLowerCase());

Assert.assertEquals("lovely girl", resultMap.get(0));
Assert.assertEquals("friendly boy", resultMap.get(1));
Assert.assertEquals("happily child", resultMap.get(2));

              // 下单用户，Queue表示正在 .排队. 抢我抢不到的二次元周边！
Queue<String> customers = new ArrayDeque<>(Arrays.asList("刑部尚书手工耿", "木瓜大盗大漠叔", "竹鼠发烧找华农", "朴实无华朱一旦"));
// 分组
List<Group> groups = Stream.iterate(0L, i -> ++i).limit(4).map(i -> Group.builder().id(i).build()).collect(Collectors.toList());
// 如你所见，它是一个map，key由用户id，value由用户组成
Map<Long, User> idUserMap = Stream.iterate(0L, i -> ++i).limit(4).map(i -> User.builder().id(i).name(customers.poll()).build()).collect(Collectors.toMap(User::getId, Function.identity()));
// 如你所见，它是一个map，key由分组id，value由用户ids组成，典型的多对多关系
Map<Long, List<Long>> groupIdUserIdsMap = groups.stream().flatMap(group -> idUserMap.keySet().stream().map(userId -> UserGroup.builder().groupId(group.getId()).userId(userId).build())).collect(Collectors.groupingBy(UserGroup::getUserId, Collectors.mapping(UserGroup::getGroupId, Collectors.toList())));

// 神奇的魔法发生了， 分组id和用户ids组成的map，竟然变成了订单编号和用户实体集合组成的map
Map<Long, List<User>> groupIdUserMap = MapUtil.change(groupIdUserIdsMap, (groupId, userIds) -> userIds.stream().map(idUserMap::get).collect(Collectors.toList()));

// 然后你就可以拿着这个map，去封装groups，使其能够在订单数据带出客户信息啦
groups.forEach(group -> Opt.ofNullable(group.getId()).map(groupIdUserMap::get).ifPresent(group::setUsers));

// 下面是测试报告
groups.forEach(group -> {
	List<User> users = group.getUsers();
	Assert.assertEquals("刑部尚书手工耿", users.get(0).getName());
	Assert.assertEquals("木瓜大盗大漠叔", users.get(1).getName());
	Assert.assertEquals("竹鼠发烧找华农", users.get(2).getName());
	Assert.assertEquals("朴实无华朱一旦", users.get(3).getName());
});
// 能写代码真开心

enum PeopleEnum {GIRL, BOY, CHILD}

@Data
@Builder
public static class User {
	private Long id;
	private String name;
}

@Data
@Builder
public static class Group {
	private Long id;
	private List<User> users;
}

@Data
@Builder
public static class UserGroup {
	private Long userId;
	private Long groupId;
}