Extract source code from .jar file

Question

Is there a way to extract the source code from an executable .jar file (Java ME)?

Unmarked

But note that doing this may be illegal depending on whether you own the copyright to the jar, the country you live in and your purpose for doing it. – Vacuous

If it is open source, get the source from the developer. Otherwise "Any compliance with the EULA will be appreciated". – Murrumbidgee

Check procyon decompiler. Download it's jar to decompile jar files. I have given steps below – Lucais

Answer 1

Use JD GUI. Open the application, drag and drop your JAR file into it.

Gaekwar

is there a way to get source code from .jar without JD GUI ? – Sirdar

@ZulqurnainJutt use as mentioned in @elachance's answer jar xf filename.jar – Julietjulieta

This is the best solution. – Facture

Answer 2

You can extract a jar file with the command :

jar xf filename.jar

References : Oracle's JAR documentation

Matlick

This is equivalent to renaming filename.jar to filename.jar.zip and then just unzipping it. – Bifoliolate

This doesn't extract the source code. It extracts the compiled source code. – Gripping

@caffinatedmonkey it does extract source code when the jar contains java files, e.g. jars with names typically ending in "-sources". It indeed does only extract .class files when the jar does not contain any java source files. – Deodorant

Answer 3

I believe this can be done very easily. You can always extract the source files (Java files) of a jar file into a zip.

Steps to get sources of a jar file as a zip :

1. Download JAD from http://techieme.in/resources-needed/ and save it at any
   location on your system.
2. Drag and drop the jar for which you want the sources on the JAD. 3 JAD UI will open with all the package structure in a tree format.
3. Click on File menu and select save jar sources.
4. It will save the sources as a zip with the same name as the jar.

Hope this helps.

The link is dead due to some reason so adding the link from where you can download the JDGUI

Draff

@Nitesh... I will be posting the link hosted on my website... please download it from there – Draff

The version in the techieme link works beautifully, thank you! – Adriel

After saving all sources, when I open the Java files, it shows all the lines as commented lines. Is there any setting to fix that? – Orpha

Answer 4

Your JAR may contain source and javadoc, in which case you can simply use jar xf my.jar to extract them.

Otherwise you can use a decompiler as mentioned in adarshr's answer:

Use JD GUI. Open the application, drag and drop your JAR file into it.

Predation

Note that .jar files are actually .zip files and can be opened with any ZIP tool. – Differentiation

Answer 5

I know it's an old question Still thought it would help someone

1) Go to your jar file's folder.

2) change it's extension to .zip.

3) You are good to go and can easily extract it by just double clicking it.

Note: I tested this in MAC, it works. Hopefully it will work on windows too.

Pristine

@JCodex, I'm doing a research project on the sentiment analysis tool "opinionfinder" and its jar does indeed contain both java AND class files. so your comment is not 100% true. I know it would usually contain only .class but not in this case at least – Dogleg

Your solution will only extract .class files not the source code. – Prayerful

Seems JD-GUI is a multi-platform tool that actually decompiles the code and shows the source code for classes in all packages. I tried it and could get the source code in a second in MacOS. I have Java 8 installed . You can get it on jd.benow.ca Not sure if it works for large projects. – Prayerful

need source code which is not provide by the way you described – Foiled

Answer 6

Do the following on your linux box where java works (if u like the terminal way of doing things)

    cd ~
    mkdir decompiled_code && cd decompiled_code
//  download jar procyon from https://drive.google.com/file/d/1yC2gJhmLoyE8royCph5dLEncgkNZXj58/view?usp=sharing
    java -jar procyon-decompiler-0.5.36.jar /Path/to/your/jar -o .

NOTE : as @Richard commented "this may be illegal depending on whether you own the copyright to the jar, the country you live in and your purpose for doing it."

Lucais

For a specific class file you can do java -jar procyon-decompiler-0.5.36.jar /Path/to/your/jar package/of/the/java/class.class > className.java – Lucais

Answer 7

Steps to get sources of a jar file as a zip :

1. Download JD-GUI from http://java-decompiler.github.io/ and save it at any location on your system.

2. Drag and drop the jar or open .jar file for which you want the sources on the JD.

3. Java Decompiler will open with all the package structure in a tree format.

4. Click on File menu and select save jar sources. It will save the sources as a zip with the same name as the jar.

Example:-

We can use Eclipse IDE for Java EE Developers as well for update/extract code if require.

From eclipse chose Import Jar and then select jar which you need. Follow instruction as per image below

Floe

Answer 8

AndroChef Java Decompiler produces very good code that you can use directly in your projects...

Mcinnis

Answer 9

Above tools extract the jar. Also there are certain other tools and commands to extract the jar. But AFAIK you cant get the java code in case code has been obfuscated.

Young

The greatest answer – Disentomb

Answer 10

suppose your JAR file is in C:\Documents and Settings\mmeher\Desktop\jar and the JAR file name is xx.jar, then write the below two commands in command prompt:

1> cd C:\Documents and Settings\mmeher\Desktop\jar

2> jar xf xx.jar

Smetana

Answer 11

-Covert .jar file to .zip (In windows just change the extension) -Unzip the .zip folder -You will get complete .java files

Shrimp

As a small note on this method... It is true that jar files are fancy zip files. However, unziping a jar will most likely yield *.class files, that is "compiled" java files. It is possible to "decompile" class files to normal java files. This functionality is included in many IDEs – Boorish

this will just unlock class files – Schechinger