jdk中bin目录详解

前言

jdk 版本 jdk1.8.0_201

编译是将java文件变为class文件，反编译是将class文件还原成java文件

javap - disassemble one or more class files ， disassemble 反汇编

一些官方的参考文档

Java Platform, Standard Edition Documentation

https://docs.oracle.com/javase/8/

Java 语言和虚拟机规范

Java ®开发工具包第 17 版工具规范

javac

javac -g + class

javac + class

javac 任意 .java文件后生成 对应的 class 文件

javap

javap + class

javap -c + class 对代码进行反汇编

javap -l + class 输出行号和本地变量表

参数为英语字母 L 不是 1 。

javap -v + class 输出附加信息

D:\ideaProject\microservices\common\src\main\java\com\example\common\basic>javap -v AutoIncrement.class
Classfile /D:/ideaProject/microservices/common/src/main/java/com/example/common/basic/AutoIncrement.class
  Last modified 2022-8-22; size 637 bytes
  MD5 checksum b38b74575c0f592187174134bd6f4cfd
  Compiled from "AutoIncrement.java"
public class com.example.common.basic.AutoIncrement
  minor version: 0
  major version: 52
  flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
   #1 = Methodref          #5.#21         // java/lang/Object."":()V
   #2 = Fieldref           #22.#23        // java/lang/System.out:Ljava/io/PrintStream;
   #3 = Methodref          #24.#25        // java/io/PrintStream.println:(I)V
   #4 = Class              #26            // com/example/common/basic/AutoIncrement
   #5 = Class              #27            // java/lang/Object
   #6 = Utf8               <init>
   #7 = Utf8               ()V
   #8 = Utf8               Code
   #9 = Utf8               LineNumberTable
  #10 = Utf8               LocalVariableTable
  #11 = Utf8               this
  #12 = Utf8               Lcom/example/common/basic/AutoIncrement;
  #13 = Utf8               main
  #14 = Utf8               ([Ljava/lang/String;)V
  #15 = Utf8               args
  #16 = Utf8               [Ljava/lang/String;
  #17 = Utf8               a
  #18 = Utf8               I
  #19 = Utf8               SourceFile
  #20 = Utf8               AutoIncrement.java
  #21 = NameAndType        #6:#7          // "":()V
  #22 = Class              #28            // java/lang/System
  #23 = NameAndType        #29:#30        // out:Ljava/io/PrintStream;
  #24 = Class              #31            // java/io/PrintStream
  #25 = NameAndType        #32:#33        // println:(I)V
  #26 = Utf8               com/example/common/basic/AutoIncrement
  #27 = Utf8               java/lang/Object
  #28 = Utf8               java/lang/System
  #29 = Utf8               out
  #30 = Utf8               Ljava/io/PrintStream;
  #31 = Utf8               java/io/PrintStream
  #32 = Utf8               println
  #33 = Utf8               (I)V
{
  public com.example.common.basic.AutoIncrement();
    descriptor: ()V
    flags: ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
         0: aload_0
         1: invokespecial #1                  // Method java/lang/Object."":()V
         4: return
      LineNumberTable:
        line 9: 0
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0       5     0  this   Lcom/example/common/basic/AutoIncrement;

  public static void main(java.lang.String[]);
    descriptor: ([Ljava/lang/String;)V
    flags: ACC_PUBLIC, ACC_STATIC
    Code:
      stack=2, locals=2, args_size=1
         0: iconst_1
         1: istore_1
         2: getstatic     #2                  // Field java/lang/System.out:Ljava/io/PrintStream;
         5: iinc          1, -1
         8: iload_1
         9: invokevirtual #3                  // Method java/io/PrintStream.println:(I)V
        12: getstatic     #2                  // Field java/lang/System.out:Ljava/io/PrintStream;
        15: iinc          1, 1
        18: iload_1
        19: invokevirtual #3                  // Method java/io/PrintStream.println:(I)V
        22: getstatic     #2                  // Field java/lang/System.out:Ljava/io/PrintStream;
        25: iload_1
        26: iinc          1, -1
        29: invokevirtual #3                  // Method java/io/PrintStream.println:(I)V
        32: getstatic     #2                  // Field java/lang/System.out:Ljava/io/PrintStream;
        35: iload_1
        36: iinc          1, 1
        39: invokevirtual #3                  // Method java/io/PrintStream.println:(I)V
        42: getstatic     #2                  // Field java/lang/System.out:Ljava/io/PrintStream;
        45: iload_1
        46: invokevirtual #3                  // Method java/io/PrintStream.println:(I)V
        49: return
      LineNumberTable:
        line 11: 0
        line 12: 2
        line 13: 12
        line 14: 22
        line 15: 32
        line 16: 42
        line 17: 49
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0      50     0  args   [Ljava/lang/String;
            2      48     1     a   I
}
SourceFile: "AutoIncrement.java"

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idea外部工具 + javap命令

如何在idea中使用 javap 命令反汇编

说明： javap命令作用于class文件，需要在target目录下存在对应的class文件，否则会报错。

我们执行 maven clean 命令后看看效果

工作目录就是 class文件存放的目录 ，正确运行截图如下所示。

java

jar

javadoc

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