如何查看class字节码文件

Posted 2020-07-21

1、使用javac编译Java文件

2、使用javap -verbose查看class字节码文件

2.1 使用-g:none或-g:lines选项来取消或要求生成LineNumberTable

2.2 使用-g:none或-g:vars选项来取消或要求生成LocalVariableTable

2.3 实例

　　D:\>javac -g:lines -g:vars Test.java

3、实例：

3.1 实例代码

public class Test {

    public int getInt(){
        int a = 1;
        return a;
    }

}

3.2 编译

D:\>javac Test.java

3.3 查看class文件

D:\>javap -verbose Test
Classfile /D:/Test.class
  Last modified 2016-6-6; size 243 bytes
  MD5 checksum a140b97d207299f2d645e25fc1552334
  Compiled from "Test.java"
public class Test
  SourceFile: "Test.java"
  minor version: 0
  major version: 51
  flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
   #1 = Methodref          #3.#12         //  java/lang/Object."<init>":()V
   #2 = Class              #13            //  Test
   #3 = Class              #14            //  java/lang/Object
   #4 = Utf8               <init>
   #5 = Utf8               ()V
   #6 = Utf8               Code
   #7 = Utf8               LineNumberTable
   #8 = Utf8               getInt
   #9 = Utf8               ()I
  #10 = Utf8               SourceFile
  #11 = Utf8               Test.java
  #12 = NameAndType        #4:#5          //  "<init>":()V
  #13 = Utf8               Test
  #14 = Utf8               java/lang/Object
{
  public Test();
    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

  public int getInt();
    flags: ACC_PUBLIC
    Code:
      stack=1, locals=2, args_size=1
         0: iconst_1
         1: istore_1
         2: iload_1
         3: ireturn
      LineNumberTable:
        line 4: 0
        line 5: 2
}