枚举类

//手动实现枚举类
//步骤
1.通过private将构造器隐藏起来
2.把这个类的所有可能的实例都使用public static final修饰的类变量来保存
3.如果有必要，可以提供一些静态方法，允许其他程序根据特定的参数来获取与之匹配的实例
public class Season{
    //把Season类定义成不可变的，将其Field也定义成final
    private final String name;
    private final String desc;
    public static final Season SPRING
        =new Season("春天","踏春");
    public static final Season SUMMER
        = new Season("夏天","炎炎");
    public static final Season FALL
        =new Season("秋天","气爽");
    public static final Season WINTER
        =new Season("冬天","赏雪");
    public static Season getSeason(int seasomNim){
        switch(seasonNum){
            case:1
                return SPRING;
                break;
            case:2
                return SUMMER;
                break;
            caes:3
                return FALL;
                break;
            case:4
                return WINTER;
                break;
            default:
                return null;
        }
    }
    //将构造器定义成private访问权限
    private Season(String name,String desc){
        this.name=name;
        this.desc=desc;
    }
    //只为name和desc提供getter方法
    public String getName(){
        return this.name;
    }
    public String getDesc(){
        return this.desc;
    }
}

//测试方法
public class SeasonTest{
    public SeasonTest(Season s){
        System.out.println(s.getName+
        s.getDesc());
    }
    public static void main(String[] args){
        //直接使用Season的FALL常量代表一个Season对象
        new SeasonTest(Season.FALL);
    }
}
//使用简单的静态常量来表示
public static final int SEASON_SPRING=1;
public static final int SEASON_SUMMER=2;
public static final int SEASON_FALL=3;
public static final int SEASON_WINTER=4;

枚举类实例：
public enum SeasonEnum{
    //在第一行列出4个枚举实例
    SPRING,SUMMER,FALL,WINTER;
}

//测试类
public class EnumTest{
    public void judge(SeasonEnum s){
        //switch语句里的表达式可以是枚举类
        switch(s){
            case SPRING:
                System.out.println("Spring");
                break;
            case SUMMER:
                System.out.println("Summer");
                break;
            case FALL:
                System.out.println("Fall");
                break;
            case WINTER:
                System.out.println("Winter");
                break;
            default:
                System.out.println("error");
        }
    } 
    public static void main(String[] args){
        //所有的枚举类都有values方法，返回该枚举类的所有实例
        for(SeasonEnum s:SeasonEnum.values()){
            System.out.println(s);
        }
        //平常使用枚举实例时，总是通过EnumClass.variable的形式访问
        new EnumTest().judge(SeasonEnum.SPRING);
    }
}