【JVM学习笔记】字节码文件结构

新建一个Java类

package com.learn.jvm;

public class MyTest1 {
    private int a = 1;

    public MyTest1() {
    }

    public int getA() {
        return this.a;
    }

    public void setA(int a) {
        this.a = a;
    }
}

在控制台使用javap -c进行反解析

D:\workspace-learn\common-learn\learn-classloader\target\classes\com\learn\jvm>javap -c MyTest1
警告: 二进制文件MyTest1包含com.learn.jvm.MyTest1
Compiled from "MyTest1.java"
public class com.learn.jvm.MyTest1 {
  public com.learn.jvm.MyTest1();
    Code:
       0: aload_0
       1: invokespecial #1                  // Method java/lang/Object."<init>":()V
       4: aload_0
       5: iconst_1
       6: putfield      #2                  // Field a:I
       9: return

  public int getA();
    Code:
       0: aload_0
       1: getfield      #2                  // Field a:I
       4: ireturn

  public void setA(int);
    Code:
       0: aload_0
       1: iload_1
       2: putfield      #2                  // Field a:I
       5: return
}

在控制台使用javap -verbose进行反解析

D:\workspace-learn\common-learn\learn-classloader\target\classes\com\learn\jvm>javap -verbose MyTest1
警告: 二进制文件MyTest1包含com.learn.jvm.MyTest1
Classfile /D:/workspace-learn/common-learn/learn-classloader/target/classes/com/learn/jvm/MyTest1.class
  Last modified 2019-9-4; size 473 bytes
  MD5 checksum 8dc78fb3801af3d26bc3befec9b7c5ed
  Compiled from "MyTest1.java"
public class com.learn.jvm.MyTest1
  SourceFile: "MyTest1.java"
  minor version: 0
  major version: 51
  flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
   #1 = Methodref          #4.#20         //  java/lang/Object."<init>":()V
   #2 = Fieldref           #3.#21         //  com/learn/jvm/MyTest1.a:I
   #3 = Class              #22            //  com/learn/jvm/MyTest1
   #4 = Class              #23            //  java/lang/Object
   #5 = Utf8               a
   #6 = Utf8               I
   #7 = Utf8               <init>
   #8 = Utf8               ()V
   #9 = Utf8               Code
  #10 = Utf8               LineNumberTable
  #11 = Utf8               LocalVariableTable
  #12 = Utf8               this
  #13 = Utf8               Lcom/learn/jvm/MyTest1;
  #14 = Utf8               getA
  #15 = Utf8               ()I
  #16 = Utf8               setA
  #17 = Utf8               (I)V
  #18 = Utf8               SourceFile
  #19 = Utf8               MyTest1.java
  #20 = NameAndType        #7:#8          //  "<init>":()V
  #21 = NameAndType        #5:#6          //  a:I
  #22 = Utf8               com/learn/jvm/MyTest1
  #23 = Utf8               java/lang/Object
{
  public com.learn.jvm.MyTest1();
    flags: ACC_PUBLIC
    Code:
      stack=2, locals=1, args_size=1
         0: aload_0
         1: invokespecial #1                  // Method java/lang/Object."<init>":()V
         4: aload_0
         5: iconst_1
         6: putfield      #2                  // Field a:I
         9: return
      LineNumberTable:
        line 8: 0
        line 9: 4
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
               0      10     0  this   Lcom/learn/jvm/MyTest1;

  public int getA();
    flags: ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
         0: aload_0
         1: getfield      #2                  // Field a:I
         4: ireturn
      LineNumberTable:
        line 12: 0
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
               0       5     0  this   Lcom/learn/jvm/MyTest1;

  public void setA(int);
    flags: ACC_PUBLIC
    Code:
      stack=2, locals=2, args_size=2
         0: aload_0
         1: iload_1
         2: putfield      #2                  // Field a:I
         5: return
      LineNumberTable:
        line 16: 0
        line 17: 5
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
               0       6     0  this   Lcom/learn/jvm/MyTest1;
               0       6     1     a   I
}