Java 枚举 单例模式 & 当作表使用

枚举是天然单例模式,所以属性添加final ,保证不会被篡改,同时去掉set方法

@ToString
@AllArgsConstructor
public enum EnumBoolean {
    /**
     * 布尔型
     */
    TRUE(1),FALSE(0);
    public final Integer value;
}

当作一个表使用:每一个变量都是一个字段。这样可以将数据库中的一些常量写在枚举中，减少IO的次数

/**
 * 山东牌照
 */
@ToString
public enum LicensePlateEnum {

    A(1, "鲁A", "济南"), B(2, "鲁B", "青岛"), C(3, "鲁C", "淄博"), D(4, "鲁D", "枣庄"),
    E(5, "鲁E", "东营"), F(6, "鲁F", "烟台"), G(7, "鲁G", "潍坊"), H(8, "鲁H", "德州"),
    J(9, "鲁J", "泰安"), K(10, "鲁K", "威海"), L(11, "鲁L", "日照"), M(12, "鲁M", "滨州"),
    N(13, "鲁N", "德州"), P(14, "鲁P", "聊城"), Q(15, "鲁Q", "临沂"), R(16, "鲁R", "菏泽"),
    U(17, "鲁U", "青岛增补"), Y(18, "鲁Y", "烟台增补");

    LicensePlateEnum(Integer code, String city, String cityName) {
        this.code = code;
        this.city = city;
        this.cityName = cityName;
    }

    @Getter
    private final Integer code;
    @Getter
    private final String city;
    @Getter
    private final String cityName;

    public static LicensePlateEnum  getByCity(String city){
        if(StringUtils.isEmpty(city)){
            return null;
        }
        for (LicensePlateEnum value : LicensePlateEnum.values()) {
            if(value.getCity().equals(city)){
                return value;
            }
        }
        return null;
    }
}

单例:
https://www.cnblogs.com/happy4java/p/11206105.html
常量表:
https://www.cnblogs.com/pzyin/p/12534640.html

end