How to extract the source code from a *.jar file on a Mac?

Question

I'm very confused. I downloaded a *.jar file as a bit of software. So, I would like to extract the source code to look at it

I used the command jar xf filename.jar

which returned two more *.jar files and a *.class file. I still cannot open these in the terminal with standard text editors.

Perhaps this is not open source software? Is there an alternative to see what has been done here?

Answer 1

• Download FernFlower.jar: http://the.bytecode.club/fernflower.jar
• Documentation: http://the.bytecode.club/fernflower.txt
• Repository: https://github.com/JetBrains/intellij-community/tree/master/plugins/java-decompiler/engine/src/org/jetbrains/java/decompiler

Run "java -jar fernflower.jar -dgs=true JarToDecompile.jar DecompiledJar"

This is what Intelli-J & Android-Studio Decompiler does.

Note: Fernflower extracts the .java files to a .jar file. You can either Unzip the jar file as a regular zip file (if your version of Archive Utility on OSX allows it -- It doesn't do it for me on OSX Sierra but works on El Capitan) OR you can do jar xf DecompiledJar and it'll extract it.

Example (all in one command -- multiple commands separated by &&):

java -jar fernflower.jar -dgs=true JarToDecompile.jar DecompiledJar && cd DecompiledJar && jar xf DecompiledJar.jar && cd ../

Answer 2

Easy solution:

If you have eclipse just add the jar file in the classpath of current project u can see all the packages and source code in the jar. You no need to install and use the commands. You will get a better view of all files