No changes after I edit a jar file

Question

Sorry if the title doesn't say what I'm trying to do very accurately but I wasn't really sure how to describe it in one sentence. Basically I have a jar file with a java file inside it, and I want to edit the java file. I used 7zip to do so and it worked, letting me edit the code in the java file. I saved it and my new code shows up when I open the java file in netbeans. However, the new code isn't actually in effect, and my program is still using the old code. I don't know if this matters, but the java file is named Templates.java, located in a package called net.sf.dynamicreports.examples in a jar named dynamicreports-examples-5.0.0-sources.jar.

Thanks in advance for any help anyone can offer.

Edit: tried importing the jar into a new project and editing from there before putting it back into the original project, but had no luck (check comment chain for further details). Still have no idea how to fix this and would greatly appreciate any help

Answer 1

Your jar contains .class files and .java files. When you create the jar, the .java files are compiled and .class files are created from them. You should have a Templates.class file that corresponds to Templates.java. When you edited Templates.java, Templates.class was never recompiled. This class file is the one your program uses. The appropriate way to change a jar file is unfortunately to regenerate the entire jar.

So, what you should do is open the code you used to create the jar in the first place, make your java changes there, and create a new jar. You will need to do this even with the smallest changes.

I didn't make the jar myself unfortunately, I got it from somewhere else so I don't have the code used to make it, just the jar itself. What should I do?

Edit: I saw your comment that you did not make the jar in the first place. This isn't too big a problem since you do have the java source code. What you need to do is copy all the .java files in the jar and make a new jar with them. Or, simply use Eclipse or whatever your favorite java editor is to compile your Templates class, and copy the new Templates.class file it creates into the appropriate place in the old jar, overwriting the old one.

Where would I find the Templates.class file?

Edit 2: You find the class file in the bin folder of your project if you are using Eclipse. See this question: Find the .class file compiled by Eclipse or if you are using a different editor/compiler, search google for where it stores its .class files.