Java-Decompiler-HOWTO.htm

<html><head><title>Java Decompiler HOW-TO</title></head><body bgcolor="white">

<hr>
<h1> Java Decompiler HOW-TO</h1>

<h2>Al Dev (Alavoor Vasudevan)        
<a href="mailto:alavoor%5BAT%5Dyahoo.com">alavoor[AT]yahoo.com</a></h2>v4.5, 20 Sep 2002
<p></p><hr>
<em>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.</em>
<hr>
<p>
</p><h2><a name="toc1">1.</a> <a href="#s1">Introduction</a></h2>

<p>
</p><h2><a name="toc2">2.</a> <a href="#s2">How can I trust Java Decompiler ??!!</a></h2>

<p>
</p><h2><a name="toc3">3.</a> <a href="#s3">Related URLs</a></h2>

<p>
</p><h2><a name="toc4">4.</a> <a href="#s4">Other Formats of this Document</a></h2>

<ul>
<li><a href="#ss4.1">4.1 Acrobat PDF format </a>
</li><li><a href="#ss4.2">4.2 Convert Linuxdoc to Docbook format </a>
</li><li><a href="#ss4.3">4.3 Convert to MS WinHelp format </a>
</li><li><a href="#ss4.4">4.4 Reading various formats </a>
</li></ul>
<p>
</p><h2><a name="toc5">5.</a> <a href="#s5">Copyright</a></h2>

<hr>
<h2><a name="s1">1.</a> <a href="#toc1">Introduction</a></h2>

<p><b>(The latest version of this document is at 
<a href="http://www.milkywaygalaxy.freeservers.com/">http://www.milkywaygalaxy.freeservers.com</a>. You may
want to check there for changes).</b>
</p><p>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).
</p><p>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.
</p><p>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 -
</p><hr>
<pre>bash$ javap -help
bash$ javap -c  &lt;filename&gt;.class
</pre>
<hr>
<p>The following are the list of Java decompilers available -
</p><ul>
<li> Free "Jad" Java Decompiler at 
<a href="http://www.geocities.com/SiliconValley/Bridge/8617/jad.html#general">http://www.geocities.com/SiliconValley/Bridge/8617/jad.html#general</a>
and at 
<a href="http://www.geocities.com/SiliconValley/Bridge/8617/jad.html#gui">http://www.geocities.com/SiliconValley/Bridge/8617/jad.html#gui</a>
<p>
</p><p>

</p></li><li> List of Decompilers, disassemblers and obfuscators are at
<a href="http://dmoz.org/Computers/Programming/Languages/Java">http://dmoz.org/Computers/Programming/Languages/Java</a>
<p>
</p><p>

</p></li><li> Free "Mocha" Java Decompiler at 
<a href="http://www.brouhaha.com/%7Eeric/computers">http://www.brouhaha.com/~eric/computers</a> and download at
<a href="http://www.brouhaha.com/%7Eeric/computers/mocha-b1.zip">http://www.brouhaha.com/~eric/computers/mocha-b1.zip</a>
<p>
</p><p>

</p></li><li> "DeCafe Pro" from DeCafe, France at 
<a href="http://decafe.hypermart.net/index.htm">http://decafe.hypermart.net/index.htm</a>
<p>
</p><p>

</p></li><li> "SourceTech Java decompiler" from Source Tech corp at 
<a href="http://www.srctec.com/">http://www.srctec.com</a> 
and at 
<a href="http://members.tripod.com/%7ESourceTec/jasmine.htm">http://members.tripod.com/~SourceTec/jasmine.htm</a>
<p>
</p><p>

</p></li><li> "SourceAgain" from Ahpah corp at 
<a href="http://www.ahpah.com/">http://www.ahpah.com</a>
<p>
</p><p>

</p></li><li> "Class Cracker" from Mayon Software, Australia at 
<a href="http://www.tip.net.au/%7Emayon/classcracker/ccorder.html">http://www.tip.net.au/~mayon/classcracker/ccorder.html</a> and at 
<a href="http://www.pcug.org.au/%7Emayon">http://www.pcug.org.au/~mayon</a>
<p>
</p><p>

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

</p></li><li> "NMI Java decompiler" from NMI at 
<a href="http://njcv.htmlplanet.com/">http://njcv.htmlplanet.com</a>
and at
<a href="http://njcv.htmlplanet.com/njcv.html">http://njcv.htmlplanet.com/njcv.html</a>
<p>
</p><p>

</p></li><li> DJ Java Decompiler at 
<a href="http://members.fortunecity.com/neshkov/dj.html">DJ decompiler</a>
or at the 
<a href="http://download.com.com/3000-2417-10146169.html?tag=must">Download.com</a>
<p>
</p><p>

</p></li><li> Google 
<a href="http://directory.google.com/Top/Computers/Programming/Languages/Java/Development_Tools/Translators/Decompilers_and_Disassemblers/?tc=1">http://directory.google.com/Top/Computers/Programming/Languages/Java/Development_Tools/Translators/Decompilers_and_Disassemblers/?tc=1</a>
<p>
</p><p>

</p></li><li> SureShot 
<a href="http://www.bysoft.se/sureshot/cavaj/index.html">http://www.bysoft.se/sureshot/cavaj/index.html</a>
and 
<a href="http://www.bysoft.se/sureshot/jcavaj/index.html">http://www.bysoft.se/sureshot/jcavaj/index.html</a>
</li>
</ul>
<p>
</p><hr>
<h2><a name="s2">2.</a> <a href="#toc2">How can I trust Java Decompiler ??!!</a></h2>

<p>For 100% assurance you need a <b>SCIENTIFIC</b> 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.
</p><p>In order to verify that the decompiler program 
is regenerating the Java source-code properly,
use the following technique -
</p><p>Generate the class file from the generated 
source code using the compiler -
</p><hr>
<pre>bash$ mv myprogram.class myprogram_orig.class
bash$ javac myprogram.java
</pre>
<hr>
<p>Now use the unix 'diff' command to compare the two class files -
</p><hr>
<pre>bash$ diff myprogram.class myprogram_orig.class
</pre>
<hr>

Both these files <b>MUST BE IDENTICAL</b>. This verifies that
decompiler program is working perfectly. On DOS or Windows 95 you may want to use
the free 
<a href="http://www.cygnus.com/">Cygnus</a> Cygwin 
'diff' or 'MKS' utilities.
<p>This step gives 100% guarantee and 100% quality assurance 
and life term or long term <b>WARRANTY</b> on decompiler programs.
</p><p>It is strongly recommended that you do these steps  
every time you run decompiler programs.
</p><hr>
<h2><a name="s3">3.</a> <a href="#toc3">Related URLs</a></h2>

<p>Visit following locators which are related to Java -
</p><ul>
<li> 
<a href="http://www.linuxdoc.org/HOWTO/Enterprise-Java-for-Linux-HOWTO.html">http://www.linuxdoc.org/HOWTO/Enterprise-Java-for-Linux-HOWTO.html</a></li>
<li> 
<a href="http://www.linuxdoc.org/HOWTO/Java-CGI-HOWTO.html">http://www.linuxdoc.org/HOWTO/Java-CGI-HOWTO.html</a></li>
<li> 
<a href="http://www.linuxdoc.org/HOWTO/JavaStation-HOWTO/index.html">http://www.linuxdoc.org/HOWTO/JavaStation-HOWTO/index.html</a></li>
<li> 
<a href="http://metalab.unc.edu/LDP/HOWTO/Vim-HOWTO.html">Vim color text editor for Java, C++, C</a></li>
<li> 
<a href="http://metalab.unc.edu/LDP/HOWTO/C-C++Beautifier-HOWTO.html">Beautifier HOWTO for Java and C++ programs</a></li>
<li> 
<a href="http://metalab.unc.edu/LDP/HOWTO/C++Programming-HOWTO.html">C++ Programming HOWTO has support for Java like String objects</a></li>
<li> Linux goodies main site is at 
<a href="http://www.milkywaygalaxy.freeservers.com/">http://www.milkywaygalaxy.freeservers.com</a> 
Mirror sites are at -
<a href="http://aldev0.webjump.com/">http://aldev0.webjump.com</a>,
<a href="http://www.angelfire.com/country/aldev0">angelfire</a>,
<a href="http://www.geocities.com/alavoor/index.html">geocities</a>,
<a href="http://aldev0.virtualave.net/">virtualave</a>,
<a href="http://aldev0.50megs.com/">50megs</a>,
<a href="http://members.theglobe.com/aldev1/index.html">theglobe</a>,
<a href="http://members.nbci.com/alavoor">NBCi</a>,
<a href="http://aldev.terrashare.com/">Terrashare</a>,
<a href="http://members.fortunecity.com/aldev">Fortunecity</a>,
<a href="http://aldev.freewebsites.com/">Freewebsites</a>,
<a href="http://members.tripod.lycos.com/aldev">Tripod</a>,
<a href="http://members.spree.com/technology/aldev">Spree</a>,
<a href="http://www.escalix.com/freepage/aldev">Escalix</a>,
<a href="http://www.httpcity.com/aldev/index.html">Httpcity</a>,
<a href="http://aldev.freeservers.com/">Freeservers</a>.
</li>
</ul>
<hr>
<h2><a name="s4">4.</a> <a href="#toc4">Other Formats of this Document</a></h2>

<p>This document is published in 14 different formats namely - DVI, Postscript, 
Latex, Adobe Acrobat PDF,
LyX, GNU-info, HTML, RTF(Rich Text Format), Plain-text, Unix man pages, single 
HTML file, SGML (Linuxdoc format), SGML (Docbook format), MS WinHelp format.
</p><p>This howto document is located at -
</p><ul>
<li> 
<a href="http://www.linuxdoc.org/">http://www.linuxdoc.org</a> and click on HOWTOs and search 
for howto document name using CTRL+f or ALT+f within the web-browser.</li>
</ul>
<p>You can also find this document at the following mirrors sites -
</p><ul>
<li> 
<a href="http://www.caldera.com/LDP/HOWTO">http://www.caldera.com/LDP/HOWTO</a></li>
<li> 
<a href="http://www.linux.ucla.edu/LDP">http://www.linux.ucla.edu/LDP</a></li>
<li> 
<a href="http://www.cc.gatech.edu/linux/LDP">http://www.cc.gatech.edu/linux/LDP</a></li>
<li> 
<a href="http://www.redhat.com/mirrors/LDP">http://www.redhat.com/mirrors/LDP</a>
</li>
<li> Other mirror sites near you (network-address-wise) can be found at
<a href="http://www.linuxdoc.org/mirrors.html">http://www.linuxdoc.org/mirrors.html</a>
select a site and go to directory /LDP/HOWTO/xxxxx-HOWTO.html</li>
</ul>
<p>
</p><p>
</p><ul>
<li>You can get this HOWTO document as a single file tar ball in HTML, DVI, 
Postscript or SGML formats from -
<a href="ftp://www.linuxdoc.org/pub/Linux/docs/HOWTO/other-formats/">ftp://www.linuxdoc.org/pub/Linux/docs/HOWTO/other-formats/</a>
and 
<a href="http://www.linuxdoc.org/docs.html#howto">http://www.linuxdoc.org/docs.html#howto</a>
<p>

</p></li><li>Plain text format is in: 
<a href="ftp://www.linuxdoc.org/pub/Linux/docs/HOWTO">ftp://www.linuxdoc.org/pub/Linux/docs/HOWTO</a>
and 
<a href="http://www.linuxdoc.org/docs.html#howto">http://www.linuxdoc.org/docs.html#howto</a>
<p>

</p></li><li>Single HTML file format is in: 
<a href="http://www.linuxdoc.org/docs.html#howto">http://www.linuxdoc.org/docs.html#howto</a>
<p> Single HTML file can be created with command (see man sgml2html) - 
sgml2html -split 0   xxxxhowto.sgml
</p><p>

</p></li><li>Translations to other languages like French, German, Spanish, 
Chinese, Japanese are in
<a href="ftp://www.linuxdoc.org/pub/Linux/docs/HOWTO">ftp://www.linuxdoc.org/pub/Linux/docs/HOWTO</a>
and 
<a href="http://www.linuxdoc.org/docs.html#howto">http://www.linuxdoc.org/docs.html#howto</a>
Any help from you to translate to other languages is welcome.</li>
</ul>

The document is written using a tool called "SGML-Tools" which can be got from - 
<a href="http://www.sgmltools.org/">http://www.sgmltools.org</a>
Compiling the source you will get the following commands like
<ul>
<li>sgml2html xxxxhowto.sgml     (to generate html file)</li>
<li>sgml2html -split 0   xxxxhowto.sgml (to generate a single page html file)</li>
<li>sgml2rtf  xxxxhowto.sgml     (to generate RTF file)</li>
<li>sgml2latex xxxxhowto.sgml    (to generate latex file)</li>
</ul>
<h2><a name="acrobatpdf"></a> <a name="ss4.1">4.1 Acrobat PDF format </a>
</h2>

<p>PDF file can be generated from postscript file using 
either acrobat <b>distill</b> or <b>Ghostscript</b>.
And postscript file is generated
from DVI which in turn is generated from LaTex file.
You can download distill software from 
<a href="http://www.adobe.com/">http://www.adobe.com</a>. Given below 
is a sample session:
</p><hr>
<pre>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 &amp;
</pre>
<hr>

Or you can use Ghostscript command <b>ps2pdf</b>.
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. 
<b>ps2pdf</b> is implemented as a very small command script 
(batch file) that invokes Ghostscript, selecting a special "output device"
called <b>pdfwrite</b>. 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.
<h2><a name="linuxdoc2docbook"></a> <a name="ss4.2">4.2 Convert Linuxdoc to Docbook format </a>
</h2>

<p>This document is written in linuxdoc SGML format. The Docbook SGML format
supercedes the linuxdoc format and has lot more features than linuxdoc.
The linuxdoc is very simple and is easy to use. To convert linuxdoc SGML 
file to Docbook SGML use the program <b>ld2db.sh</b> and some perl scripts.
The ld2db output is not 100% clean and you need to use the <b>clean_ld2db.pl</b>
perl script. You may need to manually correct few lines in the document.
</p><ul>
<li> Download ld2db program from 
<a href="http://www.dcs.gla.ac.uk/%7Errt/docbook.html">http://www.dcs.gla.ac.uk/~rrt/docbook.html</a>
or from 
<a href="http://www.milkywaygalaxy.freeservers.com/">Milkyway Galaxy site</a></li>
<li> Download the cleanup_ld2db.pl perl script from
from 
<a href="http://www.milkywaygalaxy.freeservers.com/">Milkyway Galaxy site</a></li>
</ul>

The ld2db.sh is not 100% clean, you will get lots of errors when you run
<hr>
<pre>        bash$ ld2db.sh file-linuxdoc.sgml db.sgml
        bash$ cleanup.pl db.sgml &gt; db_clean.sgml
        bash$ gvim db_clean.sgml 
        bash$ docbook2html db.sgml
</pre>
<hr>

And you may have to manually edit some of the minor errors after 
running the perl script. For e.g. you may need to put closing tag &lt;
/Para&gt; for each &lt;
Listitem&gt;
<h2><a name="mswinhelp"></a> <a name="ss4.3">4.3 Convert to MS WinHelp format </a>
</h2>

<p>You can convert the SGML howto document to Microsoft Windows Help file, 
first convert the sgml to html using:
</p><hr>
<pre>        bash$ sgml2html xxxxhowto.sgml     (to generate html file)
        bash$ sgml2html -split 0   xxxxhowto.sgml (to generate a single page html file)
</pre>
<hr>

Then use the tool 
<a href="http://javadocs.planetmirror.com/htmltohlpe.html">HtmlToHlp</a>.
You can also use sgml2rtf and then use the RTF files for generating winhelp files.
<h2><a name="readformats"></a> <a name="ss4.4">4.4 Reading various formats </a>
</h2>

<p>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 -
</p><blockquote><code>
</code><pre>        xdvi -geometry 80x90 howto.dvi
        man xdvi
</pre>
</blockquote>

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'.
<p>You can read postscript file using the program 'gv' (ghostview) or 
'ghostscript'.
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.
</p><p>
</p><ul>
<li>Get ghostscript for Windows 95, OS/2, and for 
all OSes from 
<a href="http://www.cs.wisc.edu/%7Eghost">http://www.cs.wisc.edu/~ghost</a></li>
</ul>
<p>To read postscript document give the command -
</p><blockquote><code>
</code><pre>                gv howto.ps
                ghostscript howto.ps
</pre>
</blockquote>
<p>You can read HTML format document using Netscape Navigator, Microsoft Internet
explorer, Redhat Baron Web browser or any of the 10 other web browsers.
</p><p>You can read the latex, LyX output using LyX a X-Windows front end to latex.
</p><hr>
<h2><a name="s5">5.</a> <a href="#toc5">Copyright</a></h2>

<p>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.
</p><hr>

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