How to view the source code inside a JAR file?

Question

I downloaded the code for a LAN messenger from sourceforge. It is an executable JAR file.
You double-click it and your messenger starts.

I want to study the source code. How do I do that?

score 18 · Answer 1 · edited May 23 '17 at 10:30

18

Extract source code from .jar file

(1)Use JD GUI (http://jd.benow.ca/). Open the application, drag and drop your JAR file into it.

(2)You can extract a jar file with the command :

jar xf filename.jar

References : Oracle's JAR documentation

edited May 23 '17 at 10:30

Community

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answered Feb 07 '14 at 06:22

Aruna

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score 2 · Accepted Answer · answered Jun 30 '12 at 03:29

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Sourceforge has links to the source.

answered Jun 30 '12 at 03:29

Naddiseo

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I did search sourceforge but mostly what I got was setup files. – A User Jun 30 '12 at 03:32
What's the link to the project you downloaded? – Naddiseo Jun 30 '12 at 15:52
Here: http://sourceforge.net/projects/ezim/?source=directory See if you can decompile it :) – A User Jun 30 '12 at 18:56
No need. There's a link to the source under the "code" menu. If you view the code, there's an option to download a tarball: http://ezim.svn.sourceforge.net/viewvc/ezim/ – Naddiseo Jun 30 '12 at 20:59
I tried downloading tarball but all it does is keep downloading and downloading – A User Jul 01 '12 at 04:42
sorry, my bad, done now. so the link you mentioned is all that I need now? – A User Jul 01 '12 at 05:02
Yes, it's a 26mb tarball of the source repository. – Naddiseo Jul 01 '12 at 18:45

score 2 · Answer 3 · answered Jun 30 '12 at 04:30

Opening JAR files works with any software that supports the .ZIP file format, like WinRAR.

But if you want to access the source code, it gets a little tricky as in a JAR file, the Java code is already "precompiled" into Java's byte code. Fortunately, there is a (rough) way of decompiling byte code back to (usually) readable Java source code.

There are many programs that do this, my personal favorite is JAD (http://www.varaneckas.com/jad/).

Since you found the project on sourceforge, it is likely the code is not obfuscated. Although, if it is, you can still decompile it, but it is likely to be very hard to read and comprehend.

score 1 · Answer 4 · answered Jun 30 '12 at 03:27

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do you have eclipse in your computer?you can add the jar file to a project,then you can see the source code

answered Jun 30 '12 at 03:27

andy Lau

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This is actually incorrect, you can see class code. – Tastybrownies Oct 25 '18 at 17:49

score 0 · Answer 5 · answered Nov 25 '17 at 02:37

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IntelliJ is awesome at this type of thing. Just open like you would any other project, and it will decompile it for you.

answered Nov 25 '17 at 02:37

Dave Mars

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score -1 · Answer 6 · answered Jun 30 '12 at 05:01

Only two options available 1. Use decompiler tool like Cavaj or JAD. Source might be hard to make changes to. If it for understanding the funactionality it might help. 2. SourceForge should have link to source files too. I guess it is worth trying luck to check it again on SourceForge.

How to view the source code inside a JAR file?

6 Answers6