手撕枚举类

1.什么是枚举类？

当类的对象个数有限且确定，我们认为这是枚举类

2.为什么使用枚举类？

当需要定义一组常量时，我们强烈建议使用枚举类。

3.不使用枚举类行不行？

如果类的对象只有一个，我们建议使用单例即可。

4.经典实例演示

Talk is cheap! Show me your code!

public class Test1 {

    public static void main(String[] args) {

        Season summer = Season.SUMMER;
        System.out.println(summer);
    }
}

class Season{

    //1.定义枚举类型对象的属性：需要final修饰
    private final String seasonName;
    private final String seasonDesc;

    //2.添加构造器
    public Season(String seasonName, String seasonDesc) {
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }

    //3.提供多个可以使用的枚举对象供使用
    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 + '\'' +
                '}';
    }
}

以上实例为枚举实例对象的基本写法，虽然代码较多，但是也显示出枚举的内含。

5.使用Enum方式定义枚举类

jdk5.0新增使用Enum关键字定义枚举类

//使用enum关键字枚举类
enum Season1 {
    //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;
    }

}

使用enum定义枚举类之后，如何让枚举类对象分别实现接口?

interface Info{
    void show();
}

//使用enum关键字枚举类
enum Season1 implements Info{
    //1.提供当前枚举类的对象，多个对象之间用","隔开，末尾对象";"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("宁夏");
        }
    },
    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");
        }
    };
}

来自为知笔记(Wiz)