在 C/C++ 環(huán)境下，已經(jīng)習(xí)慣使用枚舉型常量，但在 Android 下使用時(shí)發(fā)現(xiàn)枚舉與 C/C++ 下是完全不同的。

Android 下，枚舉其實(shí)是類(lèi)。
使用感覺(jué)困難，主要是枚舉與 int 之間的轉(zhuǎn)換。如果枚舉的定義如下 weekday 所示，還可以通過(guò) ordinal() 和 values()[] 方法進(jìn)行轉(zhuǎn)換。
但不幸的是，我使用的是如下 weekday_2 所示的枚舉類(lèi)型，我是沒(méi)有找到對(duì)應(yīng)的轉(zhuǎn)換方法。
最后沒(méi)有辦法，將枚舉修改為一般的常量定義，如下：

public?static?final?short?MAX_BUFFER_SIZE?=?2048;

public?class?Test?{
	public?enum?weekday
	{
	????sun,
	????mou,
	????tue,
	????thu,
	????fri,
	????sat,
	????wed,
	};
	
	public?enum?weekday_2
	{
	????sun(0x1),
	????mou(0x2),
	????tue(0x3),
	????thu(0x4),
	????fri(0x5),
	????sat(0x6),
	????wed(0x7),
	????large(0x99);		//?如果增加此值,通過(guò)?ordinal()?方法得到的值是多少？
	
	????private?int?iSet;
	????weekday_2(int?iValue)?{
	????????this.iSet?=?iValue;
	????}
	
	????public?int?Get()?{
	????????return?this.iSet;
	????}
	};
}

對(duì)于上面兩個(gè)枚舉定義 weekday 和 weekday_2:

int?x?=?weekday.sun.ordinal();
weekday?sun?=?weekday.values()[x];

與

int?x?=?weekday_2.sun.ordinal();
weekday_2?sun?=?weekday_2.values()[x];

有什么差別？除了 weekday_2 中的 large 成員外,其它成員的值是否相同？

void?TestEnumValue()?{
	TstEnum.weekday?day?=?TstEnum.weekday.sun;
	TstEnum.weekday_2?day2?=?TstEnum.weekday_2.sun;
	TstEnum.weekday_2?day2_large?=?TstEnum.weekday_2.large;
	
	int?iDay?=?day.ordinal();
	int?iDay2?=?day2.ordinal();
	int?iDay2Large?=?day2_large.ordinal();


????System.out.println("Enum?Test"?+?"value?of?sun?:?"?+?Integer.toString(iDay)?+?"/"?+?Integer.toString(iDay2)
????		+?".?Large:?"?+?Integer.toString(iDay2Large));
}

執(zhí)行后輸出的結(jié)果是: Enum Testvalue of sun : 0/0. Large: 7
weekday_2 的成員 sun 并未輸出其真實(shí)的數(shù)值，而是輸出了下標(biāo)。
對(duì)應(yīng)之，weekday.values()[x]; 也是下標(biāo)。若知道 weekday_2 的一個(gè)變量值是: 整型 0x99, 想轉(zhuǎn)成對(duì)應(yīng)的枚舉。如果使用 weekday.values()[0x99] 則會(huì)直接越界。


(1) ?執(zhí)行:javac Test.java
編譯沒(méi)有出錯(cuò)即可。


(2) 執(zhí)行: javap Test
得到以下的輸出:

Compiled?from?"Test.java"
public?class?Test?{
??int?x;
??Test$weekday?sun;
??public?Test();
}

(3) 執(zhí)行: javap Test$weekday
得到以下輸出：

Compiled?from?"Test.java"
public?final?class?Test$weekday?extends?java.lang.Enum{
??public?static?final?Test$weekday?sun;
??public?static?final?Test$weekday?mou;
??public?static?final?Test$weekday?tue;
??public?static?final?Test$weekday?thu;
??public?static?final?Test$weekday?fri;
??public?static?final?Test$weekday?sat;
??public?static?final?Test$weekday?wed;
??public?static?Test$weekday[]?values();
??public?static?Test$weekday?valueOf(java.lang.String);
??static?{};
}

(4) 執(zhí)行: javap Test$weekday_2
得到以下輸出:

Compiled?from?"Test.java"
public?final?class?Test$weekday_2?extends?java.lang.Enum{
??public?static?final?Test$weekday_2?sun;
??public?static?final?Test$weekday_2?mou;
??public?static?final?Test$weekday_2?tue;
??public?static?final?Test$weekday_2?thu;
??public?static?final?Test$weekday_2?fri;
??public?static?final?Test$weekday_2?sat;
??public?static?final?Test$weekday_2?wed;
??public?static?Test$weekday_2[]?values();
??public?static?Test$weekday_2?valueOf(java.lang.String);
??public?int?Get();
??static?{};
}

從以上反編譯出來(lái)的代碼可以得出以下結(jié)論:?
(1) weekday 和 weekday_2 枚舉類(lèi)是final class，即不能被繼承，而它本身是繼承于 Enum
(2) 枚舉值是 weekday 或 weekday_2 對(duì)象，而且是 static final 修飾的