java - 如何获取枚举的数值？

Question

假设你有

public enum Week {
    SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY
}

如何获得 int 表示星期日是 0，星期三是 3 等等？

Answer 1

Week week = Week.SUNDAY;

int i = week.ordinal();

但请注意，如果您更改声明中枚举常量的顺序，该值将会改变。解决此问题的一种方法是为所有枚举常量自分配一个 int 值，如下所示:

public enum Week 
{
     SUNDAY(0),
     MONDAY(1)

     private static final Map<Integer,Week> lookup 
          = new HashMap<Integer,Week>();

     static {
          for(Week w : EnumSet.allOf(Week.class))
               lookup.put(w.getCode(), w);
     }

     private int code;

     private Week(int code) {
          this.code = code;
     }

     public int getCode() { return code; }

     public static Week get(int code) { 
          return lookup.get(code); 
     }
}