源文件：
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package
test;public
enum EnumTest { A, B, C} |
可以看看它的字節碼(javap -v EnumTest.class > EnumTest.bytecode)：
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public
final class test.EnumTest
extends java.lang.Enum<test.EnumTest> SourceFile:
"EnumTest.java" Signature: #49
// Ljava/lang/Enum<Ltest/EnumTest;>; minor version:
0 major version:
51 flags: ACC_PUBLIC, ACC_FINAL, ACC_SUPER, ACC_ENUMConstant pool: #1
= Class #2
// test/EnumTest #2
= Utf8 test/EnumTest #3
= Class #4
// java/lang/Enum #4
= Utf8 java/lang/Enum #5
= Utf8 A #6
= Utf8 Ltest/EnumTest; #7
= Utf8 B #8
= Utf8 C #9
= Utf8 ENUM$VALUES #10
= Utf8 [Ltest/EnumTest; #11
= Utf8 <clinit> #12
= Utf8 ()V #13
= Utf8 Code #14
= String #5
// A #15
= Methodref #1.#16
// test/EnumTest."<init>":(Ljava/lang/String;I)V #16
= NameAndType #17:#18
// "<init>":(Ljava/lang/String;I)V #17
= Utf8 <init> #18
= Utf8 (Ljava/lang/String;I)V #19
= Fieldref #1.#20
// test/EnumTest.A:Ltest/EnumTest; #20
= NameAndType #5:#6
// A:Ltest/EnumTest; #21
= String #7
// B #22
= Fieldref #1.#23
// test/EnumTest.B:Ltest/EnumTest; #23
= NameAndType #7:#6
// B:Ltest/EnumTest; #24
= String #8
// C #25
= Fieldref #1.#26
// test/EnumTest.C:Ltest/EnumTest; #26
= NameAndType #8:#6
// C:Ltest/EnumTest; #27
= Fieldref #1.#28
// test/EnumTest.ENUM$VALUES:[Ltest/EnumTest; #28
= NameAndType #9:#10
// ENUM$VALUES:[Ltest/EnumTest; #29
= Utf8 LineNumberTable #30
= Utf8 LocalVariableTable #31
= Methodref #3.#16
// java/lang/Enum."<init>":(Ljava/lang/String;I)V #32
= Utf8 this #33
= Utf8 values #34
= Utf8 ()[Ltest/EnumTest; #35
= Methodref #36.#38
// java/lang/System.arraycopy:(Ljava/lang/Object;ILjava/lang/Object;II)V #36
= Class #37
// java/lang/System #37
= Utf8 java/lang/System #38
= NameAndType #39:#40
// arraycopy:(Ljava/lang/Object;ILjava/lang/Object;II)V #39
= Utf8 arraycopy #40
= Utf8 (Ljava/lang/Object;ILjava/lang/Object;II)V #41
= Utf8 valueOf #42
= Utf8 (Ljava/lang/String;)Ltest/EnumTest; #43
= Methodref #3.#44
// java/lang/Enum.valueOf:(Ljava/lang/Class;Ljava/lang/String;)Ljava/lang/Enum; #44
= NameAndType #41:#45
// valueOf:(Ljava/lang/Class;Ljava/lang/String;)Ljava/lang/Enum; #45
= Utf8 (Ljava/lang/Class;Ljava/lang/String;)Ljava/lang/Enum; #46
= Utf8 SourceFile #47
= Utf8 EnumTest.java #48
= Utf8 Signature #49
= Utf8 Ljava/lang/Enum<Ltest/EnumTest;>;{ public
static final
test.EnumTest A; flags: ACC_PUBLIC, ACC_STATIC, ACC_FINAL, ACC_ENUM public
static final
test.EnumTest B; flags: ACC_PUBLIC, ACC_STATIC, ACC_FINAL, ACC_ENUM public
static final
test.EnumTest C; flags: ACC_PUBLIC, ACC_STATIC, ACC_FINAL, ACC_ENUM static
{}; flags: ACC_STATIC Code: stack=4, locals=0, args_size=0 0:
new #1
// class test/EnumTest 3: dup
4: ldc #14
// String A 6: iconst_0
7: invokespecial #15
// Method "<init>":(Ljava/lang/String;I)V 10: putstatic #19
// Field A:Ltest/EnumTest; 13:
new #1
// class test/EnumTest 16: dup
17: ldc #21
// String B 19: iconst_1
20: invokespecial #15
// Method "<init>":(Ljava/lang/String;I)V 23: putstatic #22
// Field B:Ltest/EnumTest; 26:
new #1
// class test/EnumTest 29: dup
30: ldc #24
// String C 32: iconst_2
33: invokespecial #15
// Method "<init>":(Ljava/lang/String;I)V 36: putstatic #25
// Field C:Ltest/EnumTest; 39: iconst_3
40: anewarray #1
// class test/EnumTest 43: dup
44: iconst_0
45: getstatic #19
// Field A:Ltest/EnumTest; 48: aastore
49: dup
50: iconst_1
51: getstatic #22
// Field B:Ltest/EnumTest; 54: aastore
55: dup
56: iconst_2
57: getstatic #25
// Field C:Ltest/EnumTest; 60: aastore
61: putstatic #27
// Field ENUM$VALUES:[Ltest/EnumTest; 64:
return LineNumberTable: line
4: 0 line
3: 39 LocalVariableTable: Start Length Slot Name Signature public
static test.EnumTest[] values(); flags: ACC_PUBLIC, ACC_STATIC Code: stack=5, locals=3, args_size=0 0: getstatic #27
// Field ENUM$VALUES:[Ltest/EnumTest; 3: dup
4: astore_0
5: iconst_0
6: aload_0
7: arraylength
8: dup
9: istore_1
10: anewarray #1
// class test/EnumTest 13: dup
14: astore_2
15: iconst_0
16: iload_1
17: invokestatic #35
// Method java/lang/System.arraycopy:(Ljava/lang/Object;ILjava/lang/Object;II)V 20: aload_2
21: areturn
LineNumberTable: line
1: 0 LocalVariableTable: Start Length Slot Name Signature public
static test.EnumTest valueOf(java.lang.String); flags: ACC_PUBLIC, ACC_STATIC Code: stack=2, locals=1, args_size=1 0: ldc #1
// class test/EnumTest 2: aload_0
3: invokestatic #43
// Method java/lang/Enum.valueOf:(Ljava/lang/Class;Ljava/lang/String;)Ljava/lang/Enum; 6: checkcast #1
// class test/EnumTest 9: areturn
LineNumberTable: line
1: 0 LocalVariableTable: Start Length Slot Name Signature} |
1.它是Enum的子類。
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public
final class test.EnumTest
extends java.lang.Enum<test.EnumTest> |
2.枚舉常量是以public static final類常量的形式實現的。
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1
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public
static final test.EnumTest A; |
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1
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public
static final test.EnumTest B; |
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1
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public
static final test.EnumTest C; |
3.編譯器自動生成了values和valueOf方法。
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public
static test.EnumTest[] values(); |
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1
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public
static test.EnumTest valueOf(java.lang.String); |
很清晰，事實說明一切
