Java switch語句中用枚舉Enum

一、使用方法

在case語句中不要使用枚舉類型來引用，直接使用枚舉類型的常量名稱即可。

二、原理分析

在閱讀Java書籍和官方文檔的時候，都說Java的Switch語句是支持枚舉的，但是在網上找相關實例的時候卻沒有找到。通過查看官方文檔，明白了使用方法。
枚舉是一種static final的常量，但是在switch使用時和平時引用靜態常量有區別。因為switch條件中的枚舉類型必須和case語句里面的一致，所以當在switch語句中聲明了枚舉類型之后，case語句就已經確定了枚舉類型，所以不需要在使用枚舉類來引用了。

三、代碼示例

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

?public?class?EnumTest?{
????Day?day;????
????public?EnumTest(Day?day)?{????????this.day?=?day;
????}????
????public?void?tellItLikeItIs()?{????????switch?(day)?{????????????case?MONDAY://switch條件語句已經確定了枚舉類型，不需要再使用枚舉類型來引用枚舉常量，否則編譯出錯
????????????????System.out.println("Mondays?are?bad.");????????????????break;????????????????????
????????????case?FRIDAY:
????????????????System.out.println("Fridays?are?better.");????????????????break;?????????????????????????
????????????case?SATURDAY:?case?SUNDAY:
????????????????System.out.println("Weekends?are?best.");????????????????break;????????????????????????
????????????default:
????????????????System.out.println("Midweek?days?are?so-so.");????????????????break;
????????}
????}????
????public?static?void?main(String[]?args)?{
????????EnumTest?firstDay?=?new?EnumTest(Day.MONDAY);
????????firstDay.tellItLikeItIs();
????????EnumTest?thirdDay?=?new?EnumTest(Day.WEDNESDAY);
????????thirdDay.tellItLikeItIs();
????????EnumTest?fifthDay?=?new?EnumTest(Day.FRIDAY);
????????fifthDay.tellItLikeItIs();
????????EnumTest?sixthDay?=?new?EnumTest(Day.SATURDAY);
????????sixthDay.tellItLikeItIs();
????????EnumTest?seventhDay?=?new?EnumTest(Day.SUNDAY);
????????seventhDay.tellItLikeItIs();
????}
}

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