开发者

What does "p" in "javap" stand for?

What does "p" in "开发者_StackOverflow社区javap" stand for? (The "c" in "javac" stands for compiler)


By default, javap prints declarations of the non-private members of each of the classes specified on the command line

Reference : http://docstore.mik.ua/orelly/java/javanut/ch16_08.htm


p = print

javap is part of the official Java tools and allows to disassemble one or more class files.

The "p" in this case stands for print, as in the official documentation is reported that:

... the javap command prints the package, protected and public fields, and methods of the classes passed to it. The javap command prints its output to stdout.


it stands for java printer....


javap Official Documentation(Java 13).

p means print

As you can see, from the options description, p in javap most probably stands for print(as the helper consists MOSTLY of print this, print that, show this, show that...).

javap -help
Usage: javap <options> <classes>
where possible options include:
  -help  --help  -?        Print this usage message
  -version                 Version information
  -v  -verbose             Print additional information
  -l                       Print line number and local variable tables
  -public                  Show only public classes and members
  -protected               Show protected/public classes and members
  -package                 Show package/protected/public classes
                           and members (default)
  -p  -private             Show all classes and members
  -c                       Disassemble the code
  -s                       Print internal type signatures
  -sysinfo                 Show system info (path, size, date, MD5 hash)
                           of class being processed
  -constants               Show final constants
  -classpath <path>        Specify where to find user class files
  -cp <path>               Specify where to find user class files
  -bootclasspath <path>    Override location of bootstrap class files

As per its official documentation, the javap command prints is stated TWICE.

The javap command disassembles one or more class files. The output depends on the options used. When no options are used, then the [[HERE:]] javap command prints the package, protected and public fields, and methods of the classes passed to it. [[HERE:]] The javap command prints its output to stdout.

javap

public class CheckoutJavaP{ 
    private static int i = 1;
    protected static String s = "string";
    public static void main(String[] args){
        InnerClass iC = new InnerClass();
        iC.show();
        System.out.println(s + i);
    }
}

class InnerClass{
    protected int count;
    public InnerClass(){ System.out.println("In InnerClass Constructor");}
    public void show(){ System.out.println("In InnerClass.show()");}
    public int getCount(){ return this.count;}
}

 javap CheckoutJavaP.class
    Compiled from "CheckoutJavaP.java"
    public class CheckoutJavaP {
      protected static java.lang.String s;
      public CheckoutJavaP();
      public static void main(java.lang.String[]);
      static {};
    }

javap -v (verbose)

javap -v CheckoutJavaP.class
Classfile /C:/Users/jumping_monkey/CheckoutJavaP.class
  Last modified 9 Feb, 2020; size 822 bytes
  MD5 checksum fb7f219851715ef4489ebf7a47800d47
  Compiled from "CheckoutJavaP.java"
public class CheckoutJavaP
  minor version: 0
  major version: 52
  flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
   #1 = Methodref          #16.#30        // java/lang/Object."<init>":()V
   #2 = Class              #31            // InnerClass
   #3 = Methodref          #2.#30         // InnerClass."<init>":()V
   #4 = Methodref          #2.#32         // InnerClass.show:()V
   #5 = Fieldref           #33.#34        // java/lang/System.out:Ljava/io/PrintStream;
   #6 = Class              #35            // java/lang/StringBuilder
   #7 = Methodref          #6.#30         // java/lang/StringBuilder."<init>":()V
   #8 = Fieldref           #15.#36        // CheckoutJavaP.s:Ljava/lang/String;
   #9 = Methodref          #6.#37         // java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
  #10 = Fieldref           #15.#38        // CheckoutJavaP.i:I
  #11 = Methodref          #6.#39         // java/lang/StringBuilder.append:(I)Ljava/lang/StringBuilder;
  #12 = Methodref          #6.#40         // java/lang/StringBuilder.toString:()Ljava/lang/String;
  #13 = Methodref          #41.#42        // java/io/PrintStream.println:(Ljava/lang/String;)V
  #14 = String             #43            // string
  #15 = Class              #44            // CheckoutJavaP
  #16 = Class              #45            // java/lang/Object
  #17 = Utf8               i
  #18 = Utf8               I
  #19 = Utf8               s
  #20 = Utf8               Ljava/lang/String;
  #21 = Utf8               <init>
  #22 = Utf8               ()V
  #23 = Utf8               Code
  #24 = Utf8               LineNumberTable
  #25 = Utf8               main
  #26 = Utf8               ([Ljava/lang/String;)V
  #27 = Utf8               <clinit>
  #28 = Utf8               SourceFile
  #29 = Utf8               CheckoutJavaP.java
  #30 = NameAndType        #21:#22        // "<init>":()V
  #31 = Utf8               InnerClass
  #32 = NameAndType        #46:#22        // show:()V
  #33 = Class              #47            // java/lang/System
  #34 = NameAndType        #48:#49        // out:Ljava/io/PrintStream;
  #35 = Utf8               java/lang/StringBuilder
  #36 = NameAndType        #19:#20        // s:Ljava/lang/String;
  #37 = NameAndType        #50:#51        // append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
  #38 = NameAndType        #17:#18        // i:I
  #39 = NameAndType        #50:#52        // append:(I)Ljava/lang/StringBuilder;
  #40 = NameAndType        #53:#54        // toString:()Ljava/lang/String;
  #41 = Class              #55            // java/io/PrintStream
  #42 = NameAndType        #56:#57        // println:(Ljava/lang/String;)V
  #43 = Utf8               string
  #44 = Utf8               CheckoutJavaP
  #45 = Utf8               java/lang/Object
  #46 = Utf8               show
  #47 = Utf8               java/lang/System
  #48 = Utf8               out
  #49 = Utf8               Ljava/io/PrintStream;
  #50 = Utf8               append
  #51 = Utf8               (Ljava/lang/String;)Ljava/lang/StringBuilder;
  #52 = Utf8               (I)Ljava/lang/StringBuilder;
  #53 = Utf8               toString
  #54 = Utf8               ()Ljava/lang/String;
  #55 = Utf8               java/io/PrintStream
  #56 = Utf8               println
  #57 = Utf8               (Ljava/lang/String;)V
{
  protected static java.lang.String s;
    descriptor: Ljava/lang/String;
    flags: ACC_PROTECTED, ACC_STATIC

  public CheckoutJavaP();
    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 1: 0

  public static void main(java.lang.String[]);
    descriptor: ([Ljava/lang/String;)V
    flags: ACC_PUBLIC, ACC_STATIC
    Code:
      stack=3, locals=2, args_size=1
         0: new           #2                  // class InnerClass
         3: dup
         4: invokespecial #3                  // Method InnerClass."<init>":()V
         7: astore_1
         8: aload_1
         9: invokevirtual #4                  // Method InnerClass.show:()V
        12: getstatic     #5                  // Field java/lang/System.out:Ljava/io/PrintStream;
        15: new           #6                  // class java/lang/StringBuilder
        18: dup
        19: invokespecial #7                  // Method java/lang/StringBuilder."<init>":()V
        22: getstatic     #8                  // Field s:Ljava/lang/String;
        25: invokevirtual #9                  // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
        28: getstatic     #10                 // Field i:I
        31: invokevirtual #11                 // Method java/lang/StringBuilder.append:(I)Ljava/lang/StringBuilder;
        34: invokevirtual #12                 // Method java/lang/StringBuilder.toString:()Ljava/lang/String;
        37: invokevirtual #13                 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
        40: return
      LineNumberTable:
        line 5: 0
        line 6: 8
        line 7: 12
        line 8: 40

  static {};
    descriptor: ()V
    flags: ACC_STATIC
    Code:
      stack=1, locals=0, args_size=0
         0: iconst_1
         1: putstatic     #10                 // Field i:I
         4: ldc           #14                 // String string
         6: putstatic     #8                  // Field s:Ljava/lang/String;
         9: return
      LineNumberTable:
        line 2: 0
        line 3: 4
}
SourceFile: "CheckoutJavaP.java"


It prints the methods declarations in your class and its a very good way to see the how your compiler has interpreted your code and convert your source file into .class format.


The javap command disassembles one or more class files. Its output depends on the options used. If no options are used, javap prints out the package, protected, and public fields and methods of the classes passed to it. javap prints its output to stdout.


It lists all the methods and variable the specified class contains. You just need to paas the class name with javap command on command-line. e.g. C:\jdk1.3\bin> javap java.lang.Object it will list all the methods Object class contains.

0

上一篇:

下一篇:

精彩评论

暂无评论...
验证码 换一张
取 消

最新问答

问答排行榜