Java中如何根据父枚举值为类属性匹配分配对应的子类型枚举值

这里提供两种可行方案，均不需要修改现有CAR_ENUM、BIKE_ENUM、TRUCK_ENUM的代码：

方案一：泛型实现（首选，支持编译期类型校验） #

第一步：修改Vehicles枚举，绑定对应子枚举类型 #

public enum Vehicles {
    CAR("This is a car", CAR_ENUM.class),
    BIKE("This is a bike", BIKE_ENUM.class),
    TRUCK("This is a truck", TRUCK_ENUM.class);

    private String description;
    private Class<? extends Enum<?>> subEnumType;

    private Vehicles(String description, Class<? extends Enum<?>> subEnumType) {
        this.description = description;
        this.subEnumType = subEnumType;
    }

    public String getDescription() {
        return description;
    }

    public Class<? extends Enum<?>> getSubEnumType() {
        return subEnumType;
    }
}

第二步：定义泛型CarDealer类 #

public class CarDealer<E extends Enum<E>> {
    private Vehicles vehicle;
    private E subType;

    // 构造方法强制校验类型匹配
    public CarDealer(Vehicles vehicle, E subType) {
        if (!vehicle.getSubEnumType().isInstance(subType)) {
            throw new IllegalArgumentException(
                String.format("类型不匹配：车辆类型%s对应的子枚举应为%s",
                    vehicle.name(), vehicle.getSubEnumType().getSimpleName())
            );
        }
        this.vehicle = vehicle;
        this.subType = subType;
    }

    public Vehicles getVehicle() {
        return vehicle;
    }

    public E getSubType() {
        return subType;
    }

    public void setSubType(E subType) {
        if (!vehicle.getSubEnumType().isInstance(subType)) {
            throw new IllegalArgumentException("子枚举类型与当前车辆类型不匹配");
        }
        this.subType = subType;
    }
}

使用示例 #

// 正确用法，编译通过
CarDealer<CAR_ENUM> carDealer = new CarDealer<>(Vehicles.CAR, CAR_ENUM.SEDAN);
CarDealer<BIKE_ENUM> bikeDealer = new CarDealer<>(Vehicles.BIKE, BIKE_ENUM.SPORTS);

// 错误用法，编译直接报错
CarDealer<CAR_ENUM> wrongDealer = new CarDealer<>(Vehicles.CAR, BIKE_ENUM.CHOPPER);

方案二：非泛型实现（仅运行期校验，适合简单场景） #

如果不需要编译期强类型校验，可以直接用Object存储子枚举值，仅做运行期校验：

public class CarDealer {
    private Vehicles vehicle;
    private Object subType;

    public Vehicles getVehicle() {
        return vehicle;
    }

    public void setVehicle(Vehicles vehicle) {
        this.vehicle = vehicle;
        // 切换车辆类型时清空原有不匹配的子枚举值，可选逻辑
        this.subType = null;
    }

    public Object getSubType() {
        return subType;
    }

    public void setSubType(Object subType) {
        if (vehicle == null) {
            throw new IllegalStateException("请先设置车辆类型");
        }
        if (!vehicle.getSubEnumType().isInstance(subType)) {
            throw new IllegalArgumentException(
                String.format("子枚举类型不匹配，当前车辆类型%s对应子枚举应为%s",
                    vehicle.name(), vehicle.getSubEnumType().getSimpleName())
            );
        }
        this.subType = subType;
    }
}

内容的提问来源于stack exchange，提问作者Gu_li4n