Java Decompiler HOW-TO
 Al Dev (Alavoor Vasudevan)        [email protected]
 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.

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