枚举类（自定义 / enum）

文章目录

与接口不同，enum中的public static final是必须省去的enum继承于java.lang.Enum

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。valueOf(String str)：可以把一个字符串转为对应的枚举类对象。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： IllegalArgumentException。toString()：返回当前枚举类对象常量的名称

public class Test {
    public static void main(String[] args) {
        //values():返回所有的枚举类对象构成的数组
        Season[] values = Season.values();
        for(int i = 0;i < values.length;i++){
            System.out.println(values[i]);
        }

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

enum Season {
    SPRING,
    SUMMER,
    AUTUMN,
    WINTER
}

public class SeasonTest {
    public static void main(String[] args) {
        Season spring = Season.SPRING;
        System.out.println(spring);//输出Season类中重写的toString()，不重写的话输出地址值
    }
}

//自定义枚举类
class Season{  //注意此处是class开头
    //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;
    }
    
    //4.其他诉求1：提供toString()
    @Override
    public String toString() {
        return "Season{" +
                "seasonName='" + seasonName + ''' +
                ", seasonDesc='" + seasonDesc + ''' +
                '}';
    }
}

public class Test {
    public static void main(String[] args) {
        Season summer = Season.SUMMER;
        System.out.println(summer.toString()); //返回枚举类对象的名称
        System.out.println(Season.class.getSuperclass());//class java.lang.Enum
    }
}

//使用enum关键字枚举类
enum Season{
    //1.提供当前枚举类的对象，多个对象之间用","隔开，末尾对象";"结束
    SPRING("春天","春暖花开"),
    SUMMER("夏天","夏日炎炎"),
    AUTUMN("秋天","秋高气爽"),
    WINTER("冬天","冰天雪地");

    //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 Season(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;
    }
}

public class SeasonTest {
    public static void main(String[] args) {
        Season spring = Season.valueOf("SPRING");
        spring.show();
    }
}

interface Info{
    void show();
}

enum Season implements Info{
    SPRING(){
        @Override
        public void show() {
            System.out.println("春天在哪里？");
        }
    },
    SUMMER(){
        @Override
        public void show() {
            System.out.println("夏日炎炎");
        }
    };
}