枚举（enum）

import java.util.HashMap;
import java.util.Map;

public enum LightEnum {
    RED(1, "红灯"), YELLOW(2, "黄灯"), GREEN(3, "绿灯");
    private Integer id;
    private String description;

    private LightEnum(Integer id, String description) {
        this.id = id;
        this.description = description;
    }

    private static Map<Integer, LightEnum> idMap = new HashMap<>();
    static {
        for(LightEnum field : LightEnum.values()) {
            idMap.put(field.id, field);
        }
    }

    public static LightEnum getLightTypeById(Integer id) { return idMap.get(id);}

    public Integer getId() {
        return id;
    }
    public String getDescription() {
        return description;
    }
}