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枚举类

作者:互联网

一、枚举类的使用

  1. 枚举类的理解:类的对象只有有限个,确定的。我们称此类为枚举类。
  2. 当需要定义一组常量时,强烈建议使用枚举类。
  3. 如果枚举类中只有一个对象,则可以作为单例模式的实现方式。

二、如何定义枚举类

方式一:jdk5.0之前,自定义枚举类

//自定义枚举类
class Season {
    //1.声明Season对象的属性:private final修饰
    private final String seasonName;
    private final String seasonDesc;

    //2.私有化类的构造器,并给对象属性赋值
    private Season(String seasonName,String seasonDesc){
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }

    //3.提供当前枚举类的多个对象:public static final的
    public static final Season SPRING = new Season("春天","春暖花开");
    public static final Season SUMMER = new Season("夏天","夏日炎炎");
    public static final Season AUTUMN = new Season("秋天","秋高气爽");
    public static final Season WINTER = new Season("冬天","冰天雪地");

    //4.其他诉求1:获取枚举类对象的属性
    public String getSeasonName() {
        return seasonName;
    }

    public String getSeasonDesc() {
        return seasonDesc;
    }

    //其他诉求2:提供toString()

    @Override
    public String toString() {
        return "Season{" +
                "seasonName='" + seasonName + '\'' +
                ", seasonDesc='" + seasonDesc + '\'' +
                '}';
    }
}

方式二:jdk5.0,可以使用enum关键字定义枚举类(实现代码在最下方)

三、Enum类中的常用方法:

public class SeasonTest1 {
    public static void main(String[] args) {
        Season1 summer = Season1.SUMMER;
        //toString():
        System.out.println(summer.toString());

        System.out.println("=============================");
        //values():
        Season1[] values = Season1.values();
        for (int i = 0; i < values.length; i++) {
            System.out.println(values[i]);
            values[i].show();
        }

        //valueOf(String objName):返回枚举类中对象名是objName的对象。
        Season1 winter = Season1.valueOf("WINTER");
        //如果没有objName的枚举类对象,则抛异常:IllegalArgumentException
        //Season1 winter = Season1.valueOf("WINTER1");
        System.out.println(winter);
        winter.show();
    }
}

四、使用enum关键字定义的枚举类实现接口的情况

情况一:实现接口,在enum类中实现抽象方法
情况二:让枚举类的对象分别实现接口中的抽象方法

interface Info{
    void show();
}

//使用enum关键字定义枚举类
enum Season1 implements Info {
    //1.提供当前枚举类的对象,多个对象之间用逗号隔开,末尾对象用分号结束。
    SPRING("春天","春暖花开"){
        @Override
        public void show() {
            System.out.println("春天在哪里?");
        }
    },
    SUMMER("夏天","夏日炎炎"){
        @Override
        public void show() {
            System.out.println("夏天的风");
        }
    },
    AUTUMN("秋天","秋高气爽"){
        @Override
        public void show() {
            System.out.println("秋天不回来");
        }
    },
    WINTER("冬天","冰天雪地"){
        @Override
        public void show() {
            System.out.println("大约在冬季");
        }
    };

    //2.声明Season对象的属性:private final修饰
    private final String seasonName;
    private final String seasonDesc;

    //2.私有化类的构造器,并给对象属性赋值
    private Season1(String seasonName,String seasonDesc){
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }

    //4.其他诉求1:获取枚举类对象的属性
    public String getSeasonName() {
        return seasonName;
    }

    public String getSeasonDesc() {
        return seasonDesc;
    }
}

标签:String,Season,枚举,seasonName,seasonDesc,public
来源: https://www.cnblogs.com/koito/p/14886204.html