//Main.java
public class Main {
    
    private int m;
    
    public int inc() {
        return m + 1;
    }
}

Java(TM) SE Runtime Environment (build 1.8.0_131-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.131-b11, mixed mode)

Classfile /E:/JavaCode/TestProj/out/production/TestProj/com/rhythm7/Main.class
  Last modified 2018-4-7; size 362 bytes
  MD5 checksum 4aed8540b098992663b7ba08c65312de
  Compiled from "Main.java"
public class com.rhythm7.Main
  minor version: 0
  major version: 52
  flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
   #1 = Methodref          #4.#18         // java/lang/Object."<init>":()V
   #2 = Fieldref           #3.#19         // com/rhythm7/Main.m:I
   #3 = Class              #20            // com/rhythm7/Main
   #4 = Class              #21            // java/lang/Object
   #5 = Utf8               m
   #6 = Utf8               I
   #7 = Utf8               <init>
   #8 = Utf8               ()V
   #9 = Utf8               Code
  #10 = Utf8               LineNumberTable
  #11 = Utf8               LocalVariableTable
  #12 = Utf8               this
  #13 = Utf8               Lcom/rhythm7/Main;
  #14 = Utf8               inc
  #15 = Utf8               ()I
  #16 = Utf8               SourceFile
  #17 = Utf8               Main.java
  #18 = NameAndType        #7:#8          // "<init>":()V
  #19 = NameAndType        #5:#6          // m:I
  #20 = Utf8               com/rhythm7/Main
  #21 = Utf8               java/lang/Object
{
  private int m;
    descriptor: I
    flags: ACC_PRIVATE

  public com.rhythm7.Main();
    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 3: 0
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0       5     0  this   Lcom/rhythm7/Main;

  public int inc();
    descriptor: ()I
    flags: ACC_PUBLIC
    Code:
      stack=2, locals=1, args_size=1
         0: aload_0
         1: getfield      #2                  // Field m:I
         4: iconst_1
         5: iadd
         6: ireturn
      LineNumberTable:
        line 8: 0
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0       7     0  this   Lcom/rhythm7/Main;
}
SourceFile: "Main.java"

#1 = Methodref          #4.#18         // java/lang/Object."<init>":()V
#4 = Class              #21            // java/lang/Object
#7 = Utf8               <init>
#8 = Utf8               ()V
#18 = NameAndType        #7:#8          // "<init>":()V
#21 = Utf8               java/lang/Object

java/lang/Object."<init>":()V

#2 = Fieldref           #3.#19         // com/rhythm7/Main.m:I
#3 = Class              #20            // com/rhythm7/Main
#5 = Utf8               m
#6 = Utf8               I
#19 = NameAndType        #5:#6          // m:I
#20 = Utf8               com/rhythm7/Main

private int m;
  descriptor: I
  flags: ACC_PRIVATE

public com.rhythm7.Main();
   descriptor: ()V
   flags: ACC_PUBLIC
   Code:
     stack=1, locals=1, args_size=1
        0: aload_0 // 这条指令, 前面的0表示字节码的位置索引; 在执行跳转指令的时候, 其操作数引用的就是这种索引值(也可以叫指令偏移量), 在这里 aload_0 指令的作用, 就是将局部变量表中0号槽位的变量值(this)加载到操作数栈(压入), 供后续的其他指令使用。
        1: invokespecial #1                  // Method java/lang/Object."<init>":()V,是位置索引偏移量=1的指令, 这个指令的助记符是 invokespecial, 在字节码文件中需要附带2个字节的操作数, 也就是后面跟着的 #1 占了2个字节, 表示引用常量池中的1号item。 这条指令包括了操作码和操作数, 表示的意思是: 使用前一条指令压入操作数栈的对象, 调用特殊方法, 也就是Object类的初始化块 <init> 方法。
        4: return // 表示方法结束并返回; 为什么指令前面的索引值是4呢? 参考前一条指令的说明, 索引位置2和索引位置3, 被 invokespecial 指令的操作数占用了
     LineNumberTable:
       line 3: 0
     LocalVariableTable:
       Start  Length  Slot  Name   Signature
           0       5     0  this   Lcom/rhythm7/Main;

public int inc();                             // 方法名
    descriptor: ()I                            // 方法的描述符
    flags: ACC_PUBLIC// 方法的访问标志
    Code:       // Code开始
      stack=2, locals=1, args_size=1 // 最大栈深度、局部变量数、参数列表size
         0: aload_0// 0~6为java中的代码对应的操作码
         1: getfield      #2                  // 引用常量池#2的值，Field m:I
         4: iconst_1
         5: iadd
         6: ireturn
      LineNumberTable:   // 行号码，将上面的操作码与.java文件中的行号进行对应
        line 8: 0
      LocalVariableTable:  // 本地变量表，包括局部变量的定义
        Start  Length  Slot  Name   Signature
            0       7     0  this   Lcom/rhythm7/Main; // shot = 0， 为this

public class TestCode {
    public int foo() {
        int x;
        try {
            x = 1;
            return x;
        } catch (Exception e) {
            x = 2;
            return x;
        } finally {
            x = 3;
        }
    }
}

public int foo();
    descriptor: ()I
    flags: ACC_PUBLIC
    Code:
      stack=1, locals=5, args_size=1
         0: iconst_1 // int型1入栈 ->栈顶=1
         1: istore_1 // 将栈顶的int型数值存入第二个局部变量 ->局部2=1
         2: iload_1 // 将第二个int型局部变量推送至栈顶 ->栈顶=1
         3: istore_2 // !!将栈顶int型数值存入第三个局部变量 ->局部3=1
         
         4: iconst_3 // int型3入栈 ->栈顶=3
         5: istore_1 // 将栈顶的int型数值存入第二个局部变量 ->局部2=3
         6: iload_2 // !!将第三个int型局部变量推送至栈顶 ->栈顶=1
         7: ireturn // 从当前方法返回栈顶int数值 ->1
         
         8: astore_2 // ->局部3=Exception
         9: iconst_2 // ->栈顶=2
        10: istore_1 // ->局部2=2
        11: iload_1 // ->栈顶=2
        12: istore_3 // !! ->局部4=2
        
        13: iconst_3 // ->栈顶=3
        14: istore_1 // ->局部1=3
        15: iload_3 // !! ->栈顶=2
        16: ireturn // -> 2
        
        17: astore        4 // 将栈顶引用型数值存入第五个局部变量=any
        19: iconst_3 // 将int型数值3入栈 -> 栈顶3
        20: istore_1 // 将栈顶第一个int数值存入第二个局部变量 -> 局部2=3
        21: aload         4 // 将局部第五个局部变量(引用型)推送至栈顶
        23: athrow // 将栈顶的异常抛出
      Exception table:
         from    to  target type
             0     4     8   Class java/lang/Exception // 0到4行对应的异常，对应#8中储存的异常
             0     4    17   any // Exeption之外的其他异常
             8    13    17   any
            17    19    17   any

//SayHello.kt
package com.rhythm7

fun Any.sayHello() {
    println("Hello")
}

Classfile /E:/JavaCode/TestProj/out/production/TestProj/com/rhythm7/SayHelloKt.class
Last modified 2018-4-8; size 958 bytes
 MD5 checksum 780a04b75a91be7605cac4655b499f19
 Compiled from "SayHello.kt"
public final class com.rhythm7.SayHelloKt
 minor version: 0
 major version: 52
 flags: ACC_PUBLIC, ACC_FINAL, ACC_SUPER
Constant pool:
    // 此处省略常量池部分字节码
{
 public static final void sayHello(java.lang.Object);
   descriptor: (Ljava/lang/Object;)V
   flags: ACC_PUBLIC, ACC_STATIC, ACC_FINAL
   Code:
     stack=2, locals=2, args_size=1
        0: aload_0
        1: ldc           #9                  // String $receiver
        3: invokestatic  #15                 // Method kotlin/jvm/internal/Intrinsics.checkParameterIsNotNull:(Ljava/lang/Object;Ljava/lang/String;)V
        6: ldc           #17                 // String Hello
        8: astore_1
        9: getstatic     #23                 // Field java/lang/System.out:Ljava/io/PrintStream;
       12: aload_1
       13: invokevirtual #28                 // Method java/io/PrintStream.println:(Ljava/lang/Object;)V
       16: return
     LocalVariableTable:
       Start  Length  Slot  Name   Signature
           0      17     0 $receiver   Ljava/lang/Object;
     LineNumberTable:
       line 4: 6
       line 5: 16
   RuntimeInvisibleParameterAnnotations:
     0:
       0: #7()
}
SourceFile: "SayHello.kt"

public static final void sayHello(java.lang.Object);