java 枚举类

1.枚举类的说明：

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。

2.定义枚举类的步骤（5.0以前的）:

//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
    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：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：提供toString()

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

 

3.jdk 5.0新增使用enum定义枚举类。步骤：

//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“，”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
    private Season1(String seasonName,String seasonDesc){
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }


    //4.其他诉求：获取枚举类对象的属性

    public String getSeasonName() {
        return seasonName;
    }

    public String getSeasonDesc() {
        return seasonDesc;
    }

//    @Override
//    public void show() {
//        System.out.println("这是一个季节");
//    }
    //4.其他诉求：提供toString()

//    @Override
//    public String toString() {
//        return "Season1{" +
//                "seasonName='" + seasonName + '\'' +
//                ", seasonDesc='" + seasonDesc + '\'' +
//                '}';
//    }
}

4.使用enum定义枚举类以后，枚举类常用的方法：（继承于java.lang.Enum类）

public static void main(String[] args) {
        Season1 summer = Season1.SUMMER;
        System.out.println(summer);
        //toString()：返回枚举类对象的名称
        System.out.println(summer.toString());
        System.out.println("***********************");

        //values()：返回所有的枚举类对象构成的数组
        Season1[] values = Season1.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时objName的对象
        //如果没有objName的枚举类对象，则抛异常：IllegalArgumentException
        Season1 winter = Season1.valueOf("WINTER");
        System.out.println(winter);
    }

5.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“，”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");
        }
    };
}