Java枚举

枚举普通使用
所有定义的枚举类型均继承至抽象类Enum，Enum的构造方法是私有化的，只有编译器可以调用。

package enumdemo;

import java.util.Arrays;

public class test {

    public static void main(String[] args) {
        Day day = Day.MONDAY;
        System.out.println(day.name());
        System.out.println(day.ordinal());
        System.out.println(day.getClass());
        System.out.println(day.toString());
        System.out.println(Day.valueOf(Day.class,"MONDAY"));

        Day[] days = Day.values();
        System.out.println("days:" + Arrays.toString(days));
        System.out.println(Day.values().length);

        Enum e = Day.MONDAY;
        Class<?> clazz = e.getDeclaringClass();
        System.out.println(clazz);
         
       /**
         * 通过反射的方法获取enum实例
         */
        Day[] dsz = (Day[]) clazz.getEnumConstants();
        System.out.println(Arrays.toString(dsz));
    }

    public enum Day {
        MONDAY, TUESDAY, WEDNESDAY,
        THURSDAY, FRIDAY, SATURDAY, SUNDAY;
    }
}

输出

MONDAY
0
class enumdemo.test$Day
MONDAY
MONDAY
days:[MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY]
7
class enumdemo.test$Day
[MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY]

枚举进阶应用
在枚举中定义变量或方法

package enumdemo;


public class Day2 {

    public static void main(String[] args) {
        for (Days day : Days.values()) {
            // System.out.println(day+" "+day.desc+" "+day.getActivity());
            System.out.println(day + " " + day.getDesc() + " " + day.getActivity());
        }
    }

    public enum Days {

        MONDAY("周一", "上班"),
        TUESDAY("周二", "休息"),
        WEDNESDAY("周三", "吃斋"),
        THURSDAY("周四", "进修"),
        FRIDAY("周五", "上班"),
        SATURDAY("周六", "健身"),
        SUNDAY("周日", "徒步");

        public String desc;
        private String activity;

        /**
         * 私有化构造函数，防止被外部调用
         *
         * @param desc
         * @param activity
         */
        Days(String desc, String activity) {
            this.desc = desc;
            this.activity = activity;
        }

        public String getDesc() {
            return desc;
        }

        public String getActivity() {
            return activity;
        }

        public Days getDay(String desc){
            for(Days day : Days.values()){
                if(day.desc.equals(desc)){
                    return day;
                }
            }
            return null;
        }
    }
}

输出

MONDAY 周一 上班
TUESDAY 周二 休息
WEDNESDAY 周三 吃素
THURSDAY 周四 进修
FRIDAY 周五 上班
SATURDAY 周六 健身
SUNDAY 周日 徒步