【Eclipse】在Eclipse中使用javap指令

由於coursera課程中老師會透過javap來講解程式碼，所以這邊介紹怎麼讓Eclipse呼叫javap。

如何新增javap指令

1. 工具列點選Run ->External Tools -> External Tools Configurations
2. 右鍵點選左側欄位內的Program，選擇"New"，操作畫面如下圖
   
3. 參數設定如下：
   • Name: javap (可以自定)
   • Location: C:\Program Files\Java\jdk1.8.0_45\bin\javap.exe (底線部分請指到電腦jdk的安裝路徑)
   • Working Directory: ${workspace_loc}/${project_name}
   • Arguments: -c -verbose -classpath ${workspace_loc}/${project_name}/bin ${java_type_name}
   • 配置視窗如下圖：
     

到此就設定完成。

如何使用javap

使用javap指令時，點選工具列的Run ->External Tools -># javap (或是自定義的名稱)。

範例程式碼如下：

class JavaPConstructor

{

     int a =2000;

     JavaPConstructor(){

          this.a =3000;

     }

}

javap結果如下：

Classfile /D:/Dropbox/LunaJava/Java_week2/bin/JavaPConstructor.class

  Last modified 2015/6/15; size 325 bytes

  MD5 checksum cb4bbe5f2e1c238318c90a31ba79514a

  Compiled from "JavaPConstructor.java"

class JavaPConstructor

  minor version: 0

  major version: 52

  flags: ACC_SUPER

Constant pool:

   #1 = Class              #2             // JavaPConstructor

   #2 = Utf8               JavaPConstructor

   #3 = Class              #4             // java/lang/Object

   #4 = Utf8               java/lang/Object

   #5 = Utf8               a

   #6 = Utf8               I

   #7 = Utf8               <init>

   #8 = Utf8               ()V

   #9 = Utf8               Code

  #10 = Methodref          #3.#11         // java/lang/Object."<init>":()V

  #11 = NameAndType        #7:#8          // "<init>":()V

  #12 = Fieldref           #1.#13         // JavaPConstructor.a:I

  #13 = NameAndType        #5:#6          // a:I

  #14 = Utf8               LineNumberTable

  #15 = Utf8               LocalVariableTable

  #16 = Utf8               this

  #17 = Utf8               LJavaPConstructor;

  #18 = Utf8               SourceFile

  #19 = Utf8               JavaPConstructor.java

{

  int a;

    descriptor: I

    flags:

  JavaPConstructor();

    descriptor: ()V

    flags:

    Code:

      stack=2, locals=1, args_size=1

         0: aload_0

         1: invokespecial #10                 // Method java/lang/Object."<init>":()V

         4: aload_0

         5: sipush        2000

         8: putfield      #12                 // Field a:I

        11: aload_0

        12: sipush        3000

        15: putfield      #12                 // Field a:I

        18: return

      LineNumberTable:

        line 4: 0

        line 3: 4

        line 5: 11

        line 6: 18

      LocalVariableTable:

        Start  Length  Slot  Name   Signature

            0      19     0  this   LJavaPConstructor;

}

SourceFile: "JavaPConstructor.java"