🌈Java✨学习笔记✨ (十)面向对象——枚举的定义与使用

2.1、自定义枚举类

public class Main {

    public static void main(String[] args) {
        Season spring = Season.SPRING;
        Season summer = Season.SUMMER;
        Season autumn = Season.AUTUMN;
        Season winter = Season.WINTER;
        
        System.out.println(spring);
        System.out.println(summer);
        System.out.println(autumn);
        System.out.println(winter);
    }

}

//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 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","秋风送爽");
    public static final Season WINTER = new Season("冬天","冬虫夏草");

    //获取枚举类属性
    public String getSeasonName() {
        return seasonName;
    }

    public String getSeasonDesc() {
        return seasonDesc;
    }

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

2.2、使用enum定义枚举类

public class Main {

    public static void main(String[] args) {
        Season spring = Season.SPRING;
        Season summer = Season.SUMMER;
        Season autumn = Season.AUTUMN;
        Season winter = Season.WINTER;

        System.out.println(spring);
        System.out.println(summer);
        System.out.println(autumn);
        System.out.println(winter);
    }

}

//使用enum定义枚举类
enum  Season {
    //1、提供当前枚举类的对象,多个对象之间用逗号隔开，末尾用分号。
    SPRING("春天","春暖花开"),
    SUMMER("夏天","夏日炎炎"),
    AUTUMN("秋天","秋风送爽"),
    WINTER("冬天","冬虫夏草");

    //1、声明Season对象的属性：private final修饰
    private final String seasonName;
    private final String seasonDesc;

    //2、私有化构造器，并给对象属性赋值

    private Season(String seasonName, String seasonDesc) {
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }

    //获取枚举类属性
    public String getSeasonName() {
        return seasonName;
    }

    public String getSeasonDesc() {
        return seasonDesc;
    }

}

==定义的枚举类默认继承于java.lang.Enum类==

3、Enum类中的常用方法

Values()：返回枚举类型的对象数组。该方法可以很方便地遍历所有的枚举值

public class Main {

    public static void main(String[] args) {
        Season[] values = Season.values();
        for (Season s:values) {
            System.out.println(s);
        }
    }

}

valueOf()：可以把一个字符串转为对应地枚举类对象。要求字符串必须是枚举类对象的"名字"。如不是，会有运行时异常。

public class Main {

    public static void main(String[] args) {
    	//valueOf(String objName)：返回枚举类中对象名时objName的对象
        Season winter = Season.valueOf("WINTER");
        System.out.println(winter);
    }

}

==如果没有objName的枚举类对象，则抛异常IllegalArgumentException==

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