  Java Decompiler HOW-TO
  Al Dev (Alavoor Vasudevan)        alavoor@yahoo.com
  v3.0, 19 July 2000

  This document will help you to de-compile the Java class programs.
  This documents gives a list of decompilers which can reverse engineer
  the Java class files and generate the Java source code files.  Thie is
  very helpful if you do not have the Java source code file and have
  only the Java class files. The information in this document applies to
  all the operating sytems where Java language/Java VM runs.
  ______________________________________________________________________

  Table of Contents


  1. Introduction

  2. How can I trust Java Decompiler ??!!

  3. Related URLs

  4. Other Formats of this Document

  5. Copyright



  ______________________________________________________________________

  1.  Introduction

  Java compiler compiles the Java source code files (*.java) into
  binaries files (*.class). You would use the Java de-compiler to
  convert java class files into source code files (*.java).

  Java de-compiler is very useful especially if you have *.class files
  and you do not have access to the source code. Some vendors do not
  ship the source code for java class files, in which case you use the
  java decompiler to look at the source code.

  See also the "javap" command from Sun Microsystems. This command is
  available as soon as you install the JDK from Sun Microsystems.  At
  unix prompt type -

  ______________________________________________________________________
  bash$ javap -help
  bash$ javap -c  <filename>.class
  ______________________________________________________________________



  The following are the list of Java decompilers available -

  ·  Free "Jad" Java Decompiler at
     <http://www.geocities.com/SiliconValley/Bridge/8617/jad.html#general>
     and at
     <http://www.geocities.com/SiliconValley/Bridge/8617/jad.html#gui>



  ·  List of Decompilers, disassemblers and obfuscators are at
     <http://dmoz.org/Computers/Programming/Languages/Java>



  ·  Free "Mocha" Java Decompiler at
     <http://www.brouhaha.com/~eric/computers> and download at
     <http://www.brouhaha.com/~eric/computers/mocha-b1.zip>



  ·  "DeCafe Pro" from DeCafe, France at
     <http://decafe.hypermart.net/index.htm>



  ·  "SourceTech Java decompiler" from Source Tech corp at
     <http://www.srctec.com> and at
     <http://members.tripod.com/~SourceTec/jasmine.htm>



  ·  "SourceAgain" from Ahpah corp at  <http://www.ahpah.com>



  ·  "Class Cracker" from Mayon Software, Australia at
     <http://www.tip.net.au/~mayon/classcracker/ccorder.html> and at
     <http://www.pcug.org.au/~mayon>



  ·  "IceBreaker" from BreakerTech corp, U.K. at
     <http://www.breakertech.com> and at
     <http://www.breakertech.com/breaker/ice/ice.html#download>



  ·  "NMI Java decompiler" from NMI at <http://njcv.htmlplanet.com> and
     at <http://njcv.htmlplanet.com/njcv.html>



  2.  How can I trust Java Decompiler ??!!

  For 100% assurance you need a SCIENTIFIC way to validate and trust the
  Java Decompiler program. The method described in this section will
  enable the decompiler program to be accepted as "trust-worthy" and
  reliable.

  In order to verify that the decompiler program is regenerating the
  Java source-code properly, use the following technique -

  Generate the class file from the generated source code using the
  compiler -

  ______________________________________________________________________
  bash$ mv myprogram.class myprogram_orig.class
  bash$ javac myprogram.java
  ______________________________________________________________________



  Now use the unix 'diff' command to compare the two class files -

  ______________________________________________________________________
  bash$ diff myprogram.class myprogram_orig.class
  ______________________________________________________________________


  Both these files MUST BE IDENTICAL. This verifies that decompiler pro­
  gram is working perfectly. On DOS or Windows 95 you may want to use
  the free Cygnus <http://www.cygnus.com> Cygwin

  This step gives 100% guarantee and 100% quality assurance and life
  term or long term WARRANTY on decompiler programs.

  It is strongly recommended that you do these steps every time you run
  decompiler programs.

  3.  Related URLs

  Visit following locators which are related to Java -

  ·  <http://www.linuxdoc.org/HOWTO/Enterprise-Java-for-Linux-
     HOWTO.html>

  ·  <http://www.linuxdoc.org/HOWTO/Java-CGI-HOWTO.html>

  ·  <http://www.linuxdoc.org/HOWTO/JavaStation-HOWTO/index.html>

  ·  Vim color text editor for Java, C++, C
     <http://metalab.unc.edu/LDP/HOWTO/Vim-HOWTO.html>

  ·  Beautifier HOWTO for Java and C++ programs
     <http://metalab.unc.edu/LDP/HOWTO/C-C++Beautifier-HOWTO.html>

  ·  C++ Programming HOWTO has support for Java like String objects
     <http://metalab.unc.edu/LDP/HOWTO/C++Programming-HOWTO.html>

  ·  Linux goodies main site  <http://www.aldev.8m.com>

  ·  Linux goodies mirror site  <http://aldev.webjump.com>

  4.  Other Formats of this Document

  This document is published in 11 different formats namely - DVI,
  Postscript, Latex, Adobe Acrobat PDF, LyX, GNU-info, HTML, RTF(Rich
  Text Format), Plain-text, Unix man pages and SGML.

  ·  You can get this HOWTO document as a single file tar ball in HTML,
     DVI, Postscript or SGML formats from -
     <ftp://sunsite.unc.edu/pub/Linux/docs/HOWTO/other-formats/>

  ·  Plain text format is in:
     <ftp://sunsite.unc.edu/pub/Linux/docs/HOWTO>

  ·  Translations to other languages like French, German, Spanish,
     Chinese, Japanese are in
     <ftp://sunsite.unc.edu/pub/Linux/docs/HOWTO> Any help from you to
     translate to other languages is welcome.

     The document is written using a tool called "SGML-Tools" which can
     be got from - <http://www.sgmltools.org> Compiling the source you
     will get the following commands like

  ·  sgml2html Java-Decompiler-HOWTO.sgml     (to generate html file)

  ·  sgml2rtf  Java-Decompiler-HOWTO.sgml     (to generate RTF file)

  ·  sgml2latex Java-Decompiler-HOWTO.sgml    (to generate latex file)

  LaTeX documents may be converted into PDF files simply by producing a
  Postscript output using sgml2latex ( and dvips) and running the output
  through the Acrobat distill ( <http://www.adobe.com>) command as
  follows:
  ______________________________________________________________________
  bash$ man sgml2latex
  bash$ sgml2latex filename.sgml
  bash$ man dvips
  bash$ dvips -o filename.ps filename.dvi
  bash$ distill filename.ps
  bash$ man ghostscript
  bash$ man ps2pdf
  bash$ ps2pdf input.ps output.pdf
  bash$ acroread output.pdf &
  ______________________________________________________________________


  Or you can use Ghostscript command ps2pdf.  ps2pdf is a work-alike for
  nearly all the functionality of Adobe's Acrobat Distiller product: it
  converts PostScript files to Portable Document Format (PDF) files.
  ps2pdf is implemented as a very small command script (batch file) that
  invokes Ghostscript, selecting a special "output device" called
  pdfwrite. In order to use ps2pdf, the pdfwrite device must be included
  in the makefile when Ghostscript was compiled; see the documentation
  on building Ghostscript for details.

  This howto document is located at -

  ·  <http://sunsite.unc.edu/LDP/HOWTO/Java-Decompiler-HOWTO.html>

  Also you can find this document at the following mirrors sites -

  ·  <http://www.caldera.com/LDP/HOWTO/Java-Decompiler-HOWTO.html>

  ·  <http://www.WGS.com/LDP/HOWTO/Java-Decompiler-HOWTO.html>

  ·  <http://www.cc.gatech.edu/linux/LDP/HOWTO/Java-Decompiler-
     HOWTO.html>

  ·  <http://www.redhat.com/linux-info/ldp/HOWTO/Java-Decompiler-
     HOWTO.html>

  ·  Other mirror sites near you (network-address-wise) can be found at
     <http://sunsite.unc.edu/LDP/hmirrors.html> select a site and go to
     directory /LDP/HOWTO/Java-Decompiler-HOWTO.html


  In order to view the document in dvi format, use the xdvi program. The
  xdvi program is located in tetex-xdvi*.rpm package in Redhat Linux
  which can be located through ControlPanel | Applications | Publishing
  | TeX menu buttons.  To read dvi document give the command -


               xdvi -geometry 80x90 howto.dvi
               man xdvi



  And resize the window with mouse.  To navigate use Arrow keys, Page
  Up, Page Down keys, also you can use 'f', 'd', 'u', 'c', 'l', 'r',
  'p', 'n' letter keys to move up, down, center, next page, previous
  page etc.  To turn off expert menu press 'x'.

  You can read postscript file using the program 'gv' (ghostview) or The
  ghostscript program is in ghostscript*.rpm package and gv program is
  in gv*.rpm package in Redhat Linux which can be located through
  ControlPanel | Applications | Graphics menu buttons. The gv program is
  much more user friendly than ghostscript.  Also ghostscript and gv are
  available on other platforms like OS/2, Windows 95 and NT, you view
  this document even on those platforms.


  ·  Get ghostscript for Windows 95, OS/2, and for all OSes from
     <http://www.cs.wisc.edu/~ghost>

  To read postscript document give the command -


                       gv howto.ps
                       ghostscript howto.ps



  You can read HTML format document using Netscape Navigator, Microsoft
  Internet explorer, Redhat Baron Web browser or any of the 10 other web
  browsers.

  You can read the latex, LyX output using LyX a X-Windows front end to
  latex.

  5.  Copyright

  Copyright policy is GNU/GPL as per LDP (Linux Documentation project).
  LDP is a GNU/GPL project.  Additional requests are - you retain the
  author's name, email address and this copyright notice on all the
  copies. If you make any changes or additions to this document then you
  should intimate all the authors of this document.



