Java通过名称获取枚举常量
示例
假设我们有一个枚举DayOfWeek：
enum DayOfWeek {
SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY;
}枚举使用内置的静态valueOf()方法进行编译，该静态方法可用于按其名称查找常量：
String dayName = DayOfWeek.SUNDAY.name();
assert dayName.equals("SUNDAY");
DayOfWeek day = DayOfWeek.valueOf(dayName);
assert day == DayOfWeek.SUNDAY;使用动态枚举类型也可以这样做：
Class<DayOfWeek> enumType = DayOfWeek.class; DayOfWeek day = Enum.valueOf(enumType, "SUNDAY"); assert day == DayOfWeek.SUNDAY;
如果指定的枚举不具有名称匹配的常量，则这两种valueOf()方法都将引发IllegalArgumentException。
Guava库提供了一个辅助方法，该方法返回一个Guava以消除显式的异常处理：Enums.getIfPresent()Optional
DayOfWeek defaultDay = DayOfWeek.SUNDAY; DayOfWeek day = Enums.valueOf(DayOfWeek.class, "INVALID").or(defaultDay); assert day == DayOfWeek.SUNDAY;