比如 dotnet 的 IL
.class private auto ansi \'<Module>\' { } // end of class <Module> .class public auto ansi beforefieldinit C extends [mscorlib]System.Object { // Fields .field private initonly int32 \'<x>k__BackingField\' .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 ) // Methods .method public hidebysig specialname rtspecialname instance void .ctor () cil managed { // Method begins at RVA 0x2050 // Code size 21 (0x15) .maxstack 8 IL_0000: ldarg.0 IL_0001: ldc.i4.5 IL_0002: stfld int32 C::\'<x>k__BackingField\' IL_0007: ldarg.0 IL_0008: call instance void [mscorlib]System.Object::.ctor() IL_000d: ldarg.0 IL_000e: ldc.i4.4 IL_000f: stfld int32 C::\'<x>k__BackingField\' IL_0014: ret } // end of method C::.ctor .method public hidebysig specialname instance int32 get_x () cil managed { .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 ) // Method begins at RVA 0x2066 // Code size 7 (0x7) .maxstack 8 IL_0000: ldarg.0 IL_0001: ldfld int32 C::\'<x>k__BackingField\' IL_0006: ret } // end of method C::get_x // Properties .property instance int32 x() { .get instance int32 C::get_x() } } // end of class C比如 java 的字节码 （反编译的结果）
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"它们也是编程语言的一种，也是可以写的，所以我们可以用来把别人方法体改了。
当然怎么改，怎么改得各种各样方法都兼容，做的人简直