Learn Java for Android Development Second Edition 笔记(七）

Mastering Enums

传统枚举类型有些问题，如下例子：

class Coin{final static int PENNY = 0;final static int NICKEL = 1;final static int DIME = 2;final static int QUARTER = 3;}class Weekday{final static int SUNDAY = 0;final static int MONDAY = 1;final static int TUESDAY = 2;final static int WEDNESDAY = 3;final static int THURSDAY = 4;final static int FRIDAY = 5;final static int SATURDAY = 6;}

以上两个枚举类型变量缺乏安全检查，例如Coin.NICKEL == Weekday.MONDAY，数值上相等，但实际上不能互相比较。

Java5以后提供了一种新的数据类型enum，