java字节码文件 helloworld

时间：2022-04-14 05:54:12

Java代码

\\A.java

public class A{}
  • 1
  • 2
  • 1
  • 2

javac A.java \\得到 A.class 
javap -v A.class

下面是javap工具帮我们生成的文本的字节码文件

Classfile /home/yao/test/javap/A.class

  Last modified Aug 30, 2016; size 176 bytes

  MD5 checksum f35fe1f44d02cd491e6561a30327ceb5

  Compiled from "A.java"

public class A

  minor version: 0

  major version: 52

  flags: ACC_PUBLIC, ACC_SUPER

Constant pool:

   #1 = Methodref          #3.#10         // java/lang/Object."<init>":()V

   #2 = Class              #11            // A

   #3 = Class              #12            // java/lang/Object

   #4 = Utf8               <init>

   #5 = Utf8               ()V

   #6 = Utf8               Code

   #7 = Utf8               LineNumberTable

   #8 = Utf8               SourceFile

   #9 = Utf8               A.java

  #10 = NameAndType        #4:#5          // "<init>":()V

  #11 = Utf8               A

  #12 = Utf8               java/lang/Object

{

  public A();

    descriptor: ()V

    flags: ACC_PUBLIC

    Code:

      stack=1, locals=1, args_size=1

         0: aload_0

         1: invokespecial #1                  // Method java/lang/Object."<init>":()V

         4: return

      LineNumberTable:

        line 1: 0

}
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13
  • 14
  • 15
  • 16
  • 17
  • 18
  • 19
  • 20
  • 21
  • 22
  • 23
  • 24
  • 25
  • 26
  • 27
  • 28
  • 29
  • 30
  • 31
  • 32
  • 33
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13
  • 14
  • 15
  • 16
  • 17
  • 18
  • 19
  • 20
  • 21
  • 22
  • 23
  • 24
  • 25
  • 26
  • 27
  • 28
  • 29
  • 30
  • 31
  • 32
  • 33

不过瘾？自己按照java规范翻译一遍～

\\通过linux hexdump -C A.class 可以以16进制方式查看文件

00000000  ca fe ba be 00 00 00 34  00 0d 0a 00 03 00 0a 07  |.......4........|

00000010  00 0b 07 00 0c 01 00 06  3c 69 6e 69 74 3e 01 00  |........<init>..|

00000020  03 28 29 56 01 00 04 43  6f 64 65 01 00 0f 4c 69  |.()V...Code...Li|

00000030  6e 65 4e 75 6d 62 65 72  54 61 62 6c 65 01 00 0a  |neNumberTable...|

00000040  53 6f 75 72 63 65 46 69  6c 65 01 00 06 41 2e 6a  |SourceFile...A.j|

00000050  61 76 61 0c 00 04 00 05  01 00 01 41 01 00 10 6a  |ava........A...j|

00000060  61 76 61 2f 6c 61 6e 67  2f 4f 62 6a 65 63 74 00  |ava/lang/Object.|

00000070  21 00 02 00 03 00 00 00  00 00 01 00 01 00 04 00  |!...............|

00000080  05 00 01 00 06 00 00 00  1d 00 01 00 01 00 00 00  |................|

00000090  05 2a b7 00 01 b1 00 00  00 01 00 07 00 00 00 06  |.*..............|

000000a0  00 01 00 00 00 01 00 01  00 08 00 00 00 02 00 09  |................|

000000b0
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13

下面就按java规范来翻译一下， 
java官方字节码规范 https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.7.24

->ca fe ba be

    magic u4

->00 00 00 34

    minor_verion u2;major_version u2,jkd8

->00 0d ->13

    constant_pool_count

->#1 0a 00 03 00 0a

    [CONSTANT_METHOD] u1 tag; u2 class_index; u2 name_and_type_index

->#2 07 00 0b

    [CONSTANT_CLASS]  u1 tag; u2 name_index

->#3 07 00 0c

    [CONSTANT_CLASS]  u1 tag; u2 name_index

->#4 01 00 06 3c 69 6e 69 74 3e

    [CONSTANT_Utf8]   u1 tag; u2 length; u1[length] literal  <init>

->#5 01 00 03 28 29 56

    [CONSTANT_Utf8]   u1 tag; u2 length; u1[length] literal  ()V

->#6 01 00 04 43 6f 64 65

    [CONSTANT_Utf8]   u1 tag; u2 length; u1[length] literal  Code

->#7 01 00 0f 4c 69 6e 65 4e 75 6d 62 65 72  54 61 62 6c 65

    [CONSTANT_Utf8]   u1 tag; u2 length; u1[length] literal  LineNumberTable

->#8 01 00 0a 53 6f 75 72 63 65 46 69  6c 65

    [CONSTANT_Utf8]   u1 tag; u2 length; u1[length] literal  SourceFile

->#9 01 00 06 41 2e 6a 61 76 61

    [CONSTANT_Utf8]   u1 tag; u2 length; u1[length] literal  A.java

->#10 0c 00 04 00 05

    [CONSTANT_NAEMANDTYPE] u1 tag;u2 name_index;u2 descriptor_index;  00 04-><init> 00 05>()V

->#11 01 00 01 41

    [CONSTANT_Utf8]   u1 tag; u2 length; u1[length] literal  A

->#12 01 00 10 6a 61 76 61 2f 6c 61 6e 67  2f 4f 62 6a 65 63 74

    [CONSTANT_Utf8]   u1 tag; u2 length; u1[length] literal  java/lange/Object

->00 21

    access flag u2, ACC_PUBLIC,ACC_SUPPER

->00 02

    u2 this_class

->00 03

    u2 super_class

->00 00

    u2 interfaces count

->00 00

    u2 fields count

->00 01

    u2 methods count

{ method info #1

->00 01

    u2 access flag  public

->00 04

    u2 name index <init>

->00 05

    u2 descriptor index ()V

->00 01

    u2 attributes_count

->00 06

    u2 attribute_name_index  Code

->00 00 00 1d

    u4 attribute_length

->00 01

    u2 max_stack

->00 01

    u2 max_locals

->00 00 00 05

    u4 code_length

->2a b7 00 01 b1

    u1 code[length]

->00 00

    u2 exception_table_length;

->00 01

    u2 attributes_count

->00 07

    u2 attributes_name ->  LineNumberTable

->00 00 00 06

    u4 attributes len

->00 01

    u2 line_number_table_length

->00 00

    u2 start pc

->00 01

    u2 linue number

}

->00 01

    u2 attributes count

->00 08

    u2 attribute_name_index  > SourceFIle

->00 00 00 02

    u4 attribute_length

->00 09

    u1 info[attribute_length] 00 09 -> #9 A.java

相关文章