枚举类

  1 //手动实现枚举类
  2 //步骤
  3 1.通过private将构造器隐藏起来
  4 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
  5 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
  6 public class Season{
  7     //把Season类定义成不可变的，将其Field也定义成final
  8     private final String name;
  9     private final String desc;
 10     public static final Season SPRING
 11         =new Season("春天","踏春");
 12     public static final Season SUMMER
 13         = new Season("夏天","炎炎");
 14     public static final Season FALL
 15         =new Season("秋天","气爽");
 16     public static final Season WINTER
 17         =new Season("冬天","赏雪");
 18     public static Season getSeason(int seasomNim){
 19         switch(seasonNum){
 20             case:1
 21                 return SPRING;
 22                 break;
 23             case:2
 24                 return SUMMER;
 25                 break;
 26             caes:3
 27                 return FALL;
 28                 break;
 29             case:4
 30                 return WINTER;
 31                 break;
 32             default:
 33                 return null;
 34         }
 35     }
 36     //将构造器定义成private访问权限
 37     private Season(String name,String desc){
 38         this.name=name;
 39         this.desc=desc;
 40     }
 41     //只为name和desc提供getter方法
 42     public String getName(){
 43         return this.name;
 44     }
 45     public String getDesc(){
 46         return this.desc;
 47     }
 48 }
 49 
 50 //测试方法
 51 public class SeasonTest{
 52     public SeasonTest(Season s){
 53         System.out.println(s.getName+
 54         s.getDesc());
 55     }
 56     public static void main(String[] args){
 57         //直接使用Season的FALL常量代表一个Season对象
 58         new SeasonTest(Season.FALL);
 59     }
 60 }
 61 //使用简单的静态常量来表示
 62 public static final int SEASON_SPRING=1;
 63 public static final int SEASON_SUMMER=2;
 64 public static final int SEASON_FALL=3;
 65 public static final int SEASON_WINTER=4;
 66 
 67 枚举类实例：
 68 public enum SeasonEnum{
 69     //在第一行列出4个枚举实例
 70     SPRING,SUMMER,FALL,WINTER;
 71 }
 72 
 73 //测试类
 74 public class EnumTest{
 75     public void judge(SeasonEnum s){
 76         //switch语句里的表达式可以是枚举类
 77         switch(s){
 78             case SPRING:
 79                 System.out.println("Spring");
 80                 break;
 81             case SUMMER:
 82                 System.out.println("Summer");
 83                 break;
 84             case FALL:
 85                 System.out.println("Fall");
 86                 break;
 87             case WINTER:
 88                 System.out.println("Winter");
 89                 break;
 90             default:
 91                 System.out.println("error");
 92         }
 93     } 
 94     public static void main(String[] args){
 95         //所有的枚举类都有values方法，返回该枚举类的所有实例
 96         for(SeasonEnum s:SeasonEnum.values()){
 97             System.out.println(s);
 98         }
 99         //平常使用枚举实例时，总是通过EnumClass.variable的形式访问
100         new EnumTest().judge(SeasonEnum.SPRING);
101     }
102 }