1. 枚举类的使用

1. 枚举类的理解：类的对象只有有限个，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。

2. 如何定义枚举类

• 方式一：JDK5.0之前，自定义枚举类
• 方式二：JDK5.0以后，可以使用enum关键字定义枚举类

  2.1 自定义枚举类

class Season{
    private final String seasonName;
    private final String seasonDesc;
    
    private Season(String seasonName, String seasonDesc){
            this.seasonName = seasonName;
            this.seasonDesc = seasonDesc;
    }
    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");
    public String getSeasonName() {
        return seasonName;
    }

    public String getSeasonDesc() {
        return seasonDesc;
    }

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

　　枚举类测试：

        Season spring = Season.SPRING;
        System.out.println(spring);

2. enum关键字定义枚举类

enum Season{
    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");
    private final String seasonName;
    private final String seasonDesc;

    Season(String seasonName, String seasonDesc) {
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }
    
    public String getSeasonName() {
        return seasonName;
    }

    public String getSeasonDesc() {
        return seasonDesc;
    }
}

测试：

        System.out.println(Season.SPRING);
        System.out.println(Season.SPRING.getSeasonName());
        System.out.println(Season.SPRING.getSeasonDesc());

        Season[] seasons = Season.values();
        for (Season season : seasons) {
            System.out.println(season);
        }
        System.out.println("*********************");
        //根据名字返回对应对象
        Season spring = Season.valueOf("SPRING");
        System.out.println(spring);