Decompiling Java bytecode

Status
Released on (mm/dd/yyyy) : 02/06/2012

Description
Compiled Java classes can be decompiled if there not obfuscation during compilation step.

There several tools to do this job, one of them, free and available for several platform, is named "JAD" (http://www.varaneckas.com/jad).

How to use
JAD is a command line tool.

Command to decompile a single class
Syntax jad -sjava CLASS_FILE_NAME

Example jad -sjava Sample.class Decompile the class specified to a java file named "Sample.java" into current directory

Output // Decompiled by Jad v1.5.8g. Copyright 2001 Pavel Kouznetsov. // Jad home page: http://www.kpdus.com/jad.html // Decompiler options: packimports(3) // Source File Name:  Sample.java package com.righettod;

public class Sample {

public Sample {   } }

Command to decompile several class using file matching pattern
Syntax jad -sjava FILE_MATCHING_PATTERN

Example jad -sjava *.class Decompile all class files from the current directory to corresponding java files into current directory

Command line options
Jad v1.5.8g. Copyright 2001 Pavel Kouznetsov (jad@kpdus.com). Usage:   jad [option(s)]  Options: -a      - generate JVM instructions as comments (annotate) -af     - output fully qualified names when annotating -b      - generate redundant braces (braces) -clear  - clear all prefixes, including the default ones -d - directory for output files -dead   - try to decompile dead parts of code (if there are any) -dis    - disassembler only (disassembler) -f      - generate fully qualified names (fullnames) -ff     - output fields before methods (fieldsfirst) -i      - print default initializers for fields (definits) -l - split strings into pieces of max chars (splitstr) -lnc    - output original line numbers as comments (lnc) -lradix - display long integers using the specified radix -nl     - split strings on newline characters (splitstr) -noconv - don't convert Java identifiers into valid ones (noconv) -nocast - don't generate auxiliary casts -noclass - don't convert .class operators -nocode - don't generate the source code for methods -noctor - suppress the empty constructors -nodos  - turn off check for class files written in DOS mode -nofd   - don't disambiguate fields with the same names (nofldis) -noinner - turn off the support of inner classes -nolvt  - ignore Local Variable Table entries (nolvt) -nonlb  - don't insert a newline before opening brace (nonlb) -o      - overwrite output files without confirmation -p      - send all output to STDOUT (for piping) -pa - prefix for all packages in generated source files -pc - prefix for classes with numerical names (default: _cls) -pe - prefix for unused exception names (default: _ex) -pf - prefix for fields with numerical names (default: _fld) -pi - pack imports into one line using .* (packimports) -pl - prefix for locals with numerical names (default: _lcl) -pm - prefix for methods with numerical names (default: _mth) -pp - prefix for method parms with numerical names (default:_prm) -pv - pack fields with the same types into one line (packfields) -r      - restore package directory structure -radix - display integers using the specified radix (8, 10, or 16) -s - output file extension (default: .jad) -safe   - generate additional casts to disambiguate methods/fields -space  - output space between keyword (if, while, etc) and expression -stat   - show the total number of processed classes/methods/fields -t - use spaces for indentation (default: 4) -t      - use tabs instead of spaces for indentation -v      - show method names while decompiling -8      - convert Unicode strings into ANSI strings (ansi) -&      - redirect STDERR to STDOUT