v4.0, 14 June 2001
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.
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 -
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 -
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 program is working perfectly. On DOS or Windows 95 you may want to use
the free
Cygnus Cygwin
'diff' or 'MKS' utilities.
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.
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.
This howto document is located at -
http://www.linuxdoc.org and click on HOWTOs and search
for howto document name using CTRL+f or ALT+f within the web-browser.
You can also find this document at the following mirrors sites -
Other mirror sites near you (network-address-wise) can be found at
http://www.linuxdoc.org/mirrors.html
select a site and go to directory /LDP/HOWTO/xxxxx-HOWTO.html
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 xxxxhowto.sgml (to generate html file)
sgml2html -split 0 xxxxhowto.sgml (to generate a single page html file)
PDF file can be generated from postscript file using
either acrobat distill or Ghostscript.
And postscript file is generated
from DVI which in turn is generated from LaTex file.
You can download distill software from
http://www.adobe.com. Given below
is a sample session:
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 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 ld2db.sh and some perl scripts.
The ld2db output is not 100% clean and you need to use the clean_ld2db.pl
perl script. You may need to manually correct few lines in the document.
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 <
/Para> for each <
Listitem>
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
'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.
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.