java class file decompiler - Brave Search

How do I "decompile" Java class files? [closed]

stackoverflow.com › questions › 272535 › how-do-i-decompile-java-class-files

Update February 2016:

www.javadecompilers.com lists JAD as being:

the most popular Java decompiler, but primarily of this age only. Written in C++, so very fast.
Outdated, unsupported and does not decompile correctly Java 5 and later

So your mileage may vary with recent jdk (7, 8).

The same site list other tools.

And javadecompiler, as noted by Salvador Valencia in the comments (Sept 2017), offers a SaaS where you upload the .class file to the cloud and it returns you the decompiled code.

Original answer: Oct. 2008

The final release of JSR 176, defining the major features of J2SE 5.0 (Java SE 5), has been published on September 30, 2004.
The lastest Java version supported by JAD, the famous Java decompiler written by Mr. Pavel Kouznetsov, is JDK 1.3.
Most of the Java decompilers downloadable today from the Internet, such as “DJ Java Decompiler” or “Cavaj Java Decompiler”, are powered by JAD: they can not display Java 5 sources.

Java Decompiler (Yet another Fast Java decompiler) has:

Explicit support for decompiling and analyzing Java 5+ “.class” files.
A nice GUI:

It works with compilers from JDK 1.1.8 up to JDK 1.7.0, and others (Jikes, JRockit, etc.).

It features an online live demo version that is actually fully functional! You can just drop a jar file on the page and see the decompiled source code without installing anything.

Answer from VonC on Stack Overflow

Java Decompilers

javadecompilers.com

Java decompiler online

Java decompilers online: *JAD, *JDCore, *Procyon, *Fernflower, *CFR. ✓ A user interface to extract source code from .class and .jar ‘binary’ files.

reddit.com › r/java › looking for a java decompiler

r/java on Reddit: Looking for a Java decompiler

June 13, 2017 -

I have a couple of .jar games on my disk. I want to decompile the bytecode back to the readable .java format.

What are my options? Google wasn't very helpful, throwing old sites at me with broken download links.

I just want to learn - I played the game lots of times so I know what it does, now I want to know how it does it.

EDIT: Thanks to everyone who replied, the post stays so that others can use. I decided to use jd-gui, but it's good to know many Java IDEs have plugins to do this too (I use Netbeans and I couldn't find a decompiler plugin for it)

I've had a good experience with this one: http://jd.benow.ca/ EDIT: You decompile the .class file, which is a compiled .java file. A .jar file may contain .java files as well.

i would try fernflower from intellij ( https://github.com/JetBrains/intellij-community/tree/master/plugins/java-decompiler/engine ) for this.

Discussions

decompiler - How do I "decompile" Java class files? - Stack Overflow

What program can I use to decompile a class file? Will I actually get Java code, or is it just JVM assembly code? On Java performance questions on this site I often see responses from people who h... More on stackoverflow.com

stackoverflow.com

Decompiling a .class file - Oracle Forums

I used both programs DJ Java and cavaj to decompile a .class file. I know that when you decompile the code it generates new variable names BUT i got a lot of weird jibberish code like " if(l ==... More on forums.oracle.com

forums.oracle.com

March 19, 2008

Looking for a Java decompiler

I've had a good experience with this one: http://jd.benow.ca/ EDIT: You decompile the .class file, which is a compiled .java file. A .jar file may contain .java files as well. More on reddit.com

r/java

49

28

June 13, 2017

Decompiling/recompiling .class files

Cool, I also started looking at decompiles files today. Can you post the full command? Usually cannot find symbol errors mean something the code is referencing is missing. More on reddit.com

r/projectzomboid

4

2

March 29, 2023

Videos

Decompile Java JAR using JD-GUI tutorial for beginners - December ...

December 26, 2022

DECOMPILE Java Easily in IntelliJ or With javap - YouTube

How to Decompile Java Class Files #java #shorts - YouTube

December 17, 2022

How to decompile .jar file or .class file? | Java Decompilers & ...

August 25, 2020

The Best Java Libraries for Decompiling Class Files to Retrieve ...

January 13, 2025

Java Decompiler

java-decompiler.github.io

Java Decompiler

The “Java Decompiler project” aims to develop tools in order to decompile and analyze Java 5 “byte code” and the later versions. JD-GUI is a standalone graphical utility that displays Java source codes of “.class” files.

stackoverflow.com › questions › 272535 › how-do-i-decompile-java-class-files

decompiler - How do I "decompile" Java class files? - Stack Overflow

Update February 2016:

www.javadecompilers.com lists JAD as being:

the most popular Java decompiler, but primarily of this age only. Written in C++, so very fast.
Outdated, unsupported and does not decompile correctly Java 5 and later

So your mileage may vary with recent jdk (7, 8).

The same site list other tools.

And javadecompiler, as noted by Salvador Valencia in the comments (Sept 2017), offers a SaaS where you upload the .class file to the cloud and it returns you the decompiled code.

Original answer: Oct. 2008

The final release of JSR 176, defining the major features of J2SE 5.0 (Java SE 5), has been published on September 30, 2004.
The lastest Java version supported by JAD, the famous Java decompiler written by Mr. Pavel Kouznetsov, is JDK 1.3.
Most of the Java decompilers downloadable today from the Internet, such as “DJ Java Decompiler” or “Cavaj Java Decompiler”, are powered by JAD: they can not display Java 5 sources.

Java Decompiler (Yet another Fast Java decompiler) has:

Explicit support for decompiling and analyzing Java 5+ “.class” files.
A nice GUI:

It works with compilers from JDK 1.1.8 up to JDK 1.7.0, and others (Jikes, JRockit, etc.).

It features an online live demo version that is actually fully functional! You can just drop a jar file on the page and see the decompiled source code without installing anything.

There are a few decompilers out there... A quick search yields:

Procyon: open-source (Apache 2) and actively developed
Krakatau: open-source (GPLv3) and actively developed
CFR: open-source (MIT) and actively developed
JAD
DJ Java Decompiler
Mocha

And many more.

These produce Java code. Java comes with something that lets you see JVM byte code (javap).

Visual Studio Marketplace

marketplace.visualstudio.com › items

Decompiler for Java - Visual Studio Marketplace

Extension for Visual Studio Code - Adds a decompiler for the Java Language Support extension.

blog.andrewbeacock.com › 2006 › 10 › decompiling-java-class-files-using-jad.html

Decompiling Java .class files using JAD

AndroChef successfully decompiles obfuscated Java 6 and Java 7 .class and .jar files. It is simple but powerful tool that allows you to decompile Java and Dalvik bytecode (DEX, APK) into readable Java source.

Find elsewhere

Google Bing Mojeek

Eclipse Foundation

eclipse.org › community › eclipse_newsletter › 2017 › february › article8.php

The Features of Eclipse Class Decompiler | The Eclipse Foundation

Eclipse Class Decompiler is a plugin for the Eclipse platform. It integrates JD, Jad, FernFlower, CFR, and Procyon seamlessly with the Eclipse IDE. It displays all the Java sources during your debugging process, even if you do not have them all.

medium.com › tuanhdotnet › decompile-class-files-in-java-tools-and-techniques-82c4918324df

Decompile .class Files in Java: Tools and Techniques | by Anh Trần Tuấn | tuanhdotnet | Medium

July 11, 2025 - Decompilation translates these .class files back into human-readable .java code.

baeldung.com › home › java › decompiling classes in java

Decompiling Classes in Java | Baeldung

August 14, 2025 - java -jar JDCommandLine.jar ${TARGET_JAR_NAME}.jar ./classes · Don’t leave off the ./classes parameter. It defines the output directory. After successful decompilation, we can access the source files contained in the output directory.

intellij-support.jetbrains.com › hc › en-us › community › posts › 360008969979-How-to-use-the-Java-Bytecode-Decompiler-to-convert-class-file-to-java-file

How to use the Java Bytecode Decompiler to convert .class file to .java file – IDEs Support (IntelliJ Platform) | JetBrains

June 25, 2020 - I have a folder of class files and I would to convert them in java files. I've read through forum and one of the main responses I have found is to use the Java Bytecode Decompiler which is part of the fernflower decompiler.

forums.oracle.com › ords › apexds › post › decompiling-a-class-file-8288

Decompiling a .class file - Oracle Forums

March 19, 2008 - I used both programs DJ Java and cavaj to decompile a .class file. I know that when you decompile the code it generates new variable names BUT i got a lot of weird jibberish code like " if(l ==...

JDec - Java Decompiler Online

JDec is a online Java decompiler that provides a fast way to decompile JAR files. Instant access to the files, no need to wait. Also supports downloading decompiled java code.

github.com › mstrobel › procyon › wiki › Java-Decompiler

Java Decompiler

October 27, 2019 - I will work to improve support for other compilers as time goes on. The Procyon decompiler handles language enhancements from Java 5 and beyond that most other decompilers don't. It also excels in areas where others fall short.

Author mstrobel

Java Code Geeks

javacodegeeks.com › home › core java

13 Best Java Decompilers for Download and Online Use for Java Developers - Java Code Geeks

November 17, 2021 - JDProject is the most used java decompiler in the world by java developers because it has the support for the Eclipse IDE and offline tool as well. This one is easy to use and supports java 1.1 onwards.

jetbrains.com › help › idea › decompiler.html

Bytecode decompiler | IntelliJ IDEA Documentation

February 23, 2026 - Open the Installed tab, find the Java Bytecode Decompiler plugin, and select the checkbox next to the plugin name. Open a compiled .class file in the editor.

github.com › java-decompiler › jd-gui

GitHub - java-decompiler/jd-gui: A standalone Java Decompiler GUI · GitHub

JD-GUI, a standalone graphical utility that displays Java sources from CLASS files. Java Decompiler projects home page: http://java-decompiler.github.io

Starred by 15.1K users

Forked by 2.5K users

Languages Java 96.3% | ANTLR 2.3% | Shell 1.4%

codemia.io › knowledge-hub › path › how_do_i_decompile_java_class_files

How do I decompile Java class files?

Enhance your system design skills with over 120 practice problems, detailed solutions, and hands-on exercises

digitalocean.com › community › tutorials › java-compiler

Java Decompiler Explained: How It Works, Tools, and Use Cases | DigitalOcean

June 19, 2025 - Parse .class file structure (constant pool, methods, fields) ... Tip: If you use IntelliJ IDEA or Eclipse, plugins like Fernflower and Enhanced Class Decompiler make the process seamless. Need something quick and accessible? Online Java decompilers let you view the contents of .class files without downloading any software.

Raspberry Pi Forums

forums.raspberrypi.com › board index › programming › java

How to decrypt a .class file - Raspberry Pi Forums

Use jadx. With that you can decompile both dex, jar and class-files. Download at https://github.com/skylot/jadx · “Knock, knock.” - “Who’s there?” - very long pause…. - “Java.” If a python knocks on your door and says “Hi, I’m a vacuum cleaner!” it’s not true.

Notepad++ Community

community.notepad-plus-plus.org › topic › 23253 › can-you-add-java-class-file-decompiler-plugin

Can you add java .class file decompiler plugin? | Notepad++ Community

July 19, 2022 - # -*- coding: utf-8 -*- from __future__ import print_function # for py 2.7 import sys import subprocess import tempfile from os import path from Npp import notepad """ Shells out to the Procyon decompiler and opens the generated source in Notepad++ ...