源文件：
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package
test;
public
enum
EnumTest {
A, B, C
}
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可以看看它的字节码(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_ENUM
Constant 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;
#
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= 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
}
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1.它是Enum的子类。
|
1
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public
final
class
test.EnumTest
extends
java.lang.Enum<test.EnumTest>
|
2.枚举常量是以public static final类常量的形式实现的。
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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;
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3.编译器自动生成了values和valueOf方法。
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1
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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);
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很清晰，事实说明一切