How to Edit and Compile Java Jar Files

In this video I show a basic and simple process to edit and make changes to a JAR file. I use the following Java Decompiler to de-compile the class files in the jar file.
Java Decompiler (JD-GUI): java-decompiler...
What is a JAR File?
A JAR is a package file format typically used to aggregate many Java class files and associated metadata and resources into one file for distribution. JAR files are archive files that include a Java-specific manifest file. They are built on the ZIP format and typically have a .jar file extension.
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Thanks.

[@AzaleaTFG]

thank you, i wanted to make a simple change and all the reddit resources kept saying don't do it because you will mess up, but its just changing a mods units and adding a few files.

[@kylecaudill9261]

Thank you. I look forward to editing my game files.

[@GetCrouchedOnNerd]

My minecraft world looks loke the biblically accurate angels now

[@埊]

@@GetCrouchedOnNerd Enchantcally accurate worlds

[@CinemaIsG0ne]

same!!

[@chaunceywei8430]

if this class doesn't have relation with other jar , this is a good method. otherwise , you will get a lot of error while you compiler the java file to class file

[@FBI_Agent_]

So anyone getting the errors here is what you do; Move the .java files to the ORIGINAL FILE LOCATION where all your .jar .zip and _class and _java files are then open cmd as he does in the video and run the command as he does and if your getting errors still do the -classpath (Then the name of your decompiled.jar file).

[@jiocrestfall]

i followed the steps and kept going fine up til i needed to compile the java file i wanted to edit: a hundred errors being shown out of 300+ saying "item does not exist" for almost all the lines
pls help :

[@jcz8225]

Hola, me pasa lo mismo, has encontrado alguna solucion?

[@grammor]

@@jcz8225 te voy a ser completamente honesto, no esta bien decir "has encontrado la solucion?" porque cuando queremos recibir una notificacion o ver un mensaje de respuesta es para esperar la respuesta o solución del problema se vuelve molesto recibir este tipo de mensajes

[@niceone9805]

@@grammor callate tonto xD

[@BonnGamer257]

@@grammor flaco esta preguntando si tuvo solución para saber si lo pueden ayudar también a el no rompas los huevos

[@da_goose_gang]

may be a dumb question, but at 5:12 i litterally dont have the option to extract it, any idea what to do?

[@yJoh_]

Download WinRar

[@AdrielLoboz]

Followed your tutorial step-by-step, ended up getting 178 errors... no clue what I did wrong

[@sankeths3508]

simple video which added great value, thanks very much sir

[@iteducator]

Thank you, You're welcome

[@jcz8225]

@@iteducator tengo errores en el momento de usar javac y
@jiocrestfall tambien

[@goodbye9809]

The files extracted for class are slightly different than when extracted for java, when I open the class files and go to the one I want to edit, multiple files appear that are not in the java files, when I copy my java file into the class file and delete said class file for javac I get error "cannot find symbol". any help?

[@Pelota480]

When I tried using the javac part, I get a bunch of errors and cant generate .class

[@leonardorosadossantos9876]

same

[@RoyLye]

You probably need to add the classpath javac -cp

[@ardaonuk2790]

@@RoyLye still got same error

[@ardaonuk2790]

@@RoyLye got the same error. you meant the jar file for unpacked file?

[@iteducator]

you need to keep all the dependencies as well used in the java file

[@Bottle_of_airYT]

I dont undertsand what you did when extractin ghr jar file, it doesnt work, im on windows 11

[@googologyx]

I tried the javac command on a bunch of files in my Minecraft JAR file and it came back with a handful of errors

[@ardaonuk2790]

did you fix it?

[@googologyx]

@@ardaonuk2790 I did not

[@iteducator]

You shoud keep all the dependencies as well used in the java file

[@FreeCrazyIce]

check if the jar file is a zip, if not, idk how to help with that

[@DasherShortsYT]

Issue when I try to recompile is it gives a bunch of errors about cannot finds symbol. Looking through replies, I don't understand what you mean by "make sure all dependencies are there."

[@padlock2257]

Hi i get error when compiling. without changing anything from the .java file

[@iteducator]

please make sure all the imports are also present in the extracted folder

[@ob0-china]

@@iteducator do you mean that if the decompiled class file imports from other packages, i have to copy the packages into the same folder?

[@justnormal2you455]

Thanks man, imma decompile a java phone game and modify shit, thansk again!

[@iteducator]

great

[@yers7638]

Nice i can decompile files but i dont know how to recompile them nice tutorial!

[@iteducator]

You can follow the tutorial, if there is any problem.

[@埊]

@@iteducator which tutorial, it doesnt work too

[@chrispharaoh4838]

I liked your video very much it answered my question

[@iteducator]

Thank you

[@AD-je9nq]

Hello , this is such a great Video , thank YOU Very much for sharing , really appreciate it brother
i had a quick question for you , my code is in in the jar ,but weird is its under a folder WEB-INF and Javac is giVing errors and not compiling
it says package does not exist for WEB-INF ...what do we do now ? how can we compile ? please please help brother
thank you
Ajay

[@mostdefinitelyahuman6875]

so I used javac, but it gave me an error saying "'javac' is not recognized as an internal or external command, operable program or batch file." Am I missing something?

[@chaunceywei8430]

you need to add Environment Variables for JDK

[@Red-ne]

getting bunch of erros when trying the javac command

[@iteducator]

you have to place all the class files required for compilation

[@askaine]

​@@iteducator you mean if i changes multiple files i need to copy and paste them all and then do the javac command?

[@iteducator]

yes all the imported classes and its dependent classes should be present as the compiler will use them.

[@tonyfuentes9321]

Than you bro
Question can you make a video explaining the obfuscated and de-obfuscated java files
Please thank you

[@iteducator]

Thanks, sure I'll try.

[@oFaiOfficial]

How do I Like Change a PNG There is one how do i replace it???

[@iteducator]

try winrar to add or delete, keep the same file name.

[@oFaiOfficial]

@@iteducator Oh I Actually Managed to do it a while ago But One Thing. so How do I Change it when Like the File Opens (Im Customizing a Minecraft Client) The Name of it is at the corner of the window how do I Change that?

[@KarmaFight]

Thanks a lot, It helped me a lot

[@iteducator]

Glad to hear that

[@Elphoquito]

cant return into .Class file i get error in cmd

[@iteducator]

please make sure all the imports are also present in the extracted folder

[@banglagaming007]

When I am going to open a jar file through jd gui, it just doesn't open!!!
What should I do now???

[@iteducator]

Extract the jar and then open any class file as a workaround, it does not happen usually unless something is wrong with the jar file.

[@GokulRaj-iz3by]

Bro if re complied I getting error in the progam showing some is not available

[@iteducator]

yes all the imported dependencies must be placed in the same paths as well to compile the code

[@GokulRaj-iz3by]

@@iteducator your great . It works fine, thanks a lot. Please keep helping people. No words to say.

[@ravikiranmutta1124]

its taking much time to convert source code for my respective jar file. more than 1 hr still not converted

[@iteducator]

if the jar file is too large, it can be an issue, try doing it in parts

[@ravikiranmutta1124]

Tqs for suggestions will try with that.

[@rooverr]

error: ')' or ',' expected
}1L, 10L);
^
how do I fix this ( this happened after I typed in the javac command )

[@iteducator]

check the java code in some editor, there seems to be a missing closing bracket

[@tanvirremix]

success

[@plamen-vw4bm]

it says java isnt recognized as an internal or external command, operable program or batch file

[@iteducator]

It's javac. And have you installed java in your system?

[@plamen-vw4bm]

@@iteducator yes it works now but i get 112 errors when i try to compile it

[@iteducator]

You will have to resolve the programming errors. And make sure all the packages being used are present in the same paths as in the jar

[@lawjz6927]

@@iteducator bro i installed java but i cant use javac command its jdk8 1.80 vers

[@iteducator]

@@lawjz6927 check if java is installed properly, type java -version in the command line

[@droidlycodes]

Ran this and it runs a bunch of errors when compiling is there a method to avoid this?

[@iteducator]

You must have all the dependency packages as well for it to compile

[@dongwn13]

'javac' is not recognized as an internal or external command,
operable program or batch file.
How to resolve this??

[@iteducator]

You must have Java JDK installed.
ruclips.net/video/i21CvFuDxek/видео.html

[@bharathreddygajjala]

How do I add other package references to compile. I have dependency on other jar/packages.

[@iteducator]

keep them in the same folder as java files, and the entire folder structure should be the same as the JAR

[@patricklee3735]

saved my day! much appreciated!

[@iteducator]

Glad it helped!

[@GooseAlarm]

what if the file you want to edit is a .json?

[@iteducator]

JSON can be edited as it is.

[@music8d53]

currently i don't switch from java to class using CMD . How to fix?

[@iteducator]

how can you switch in cmd? I don't understand your point

[@MS-cn4dh]

Hi.. I followed these steps but when I do javac filename.java in cmd, it gives me 5 errors. The errors are: cannot find Symbol (for class names). How to resolve this???

[@iteducator]

It occurs when you have the wrong keyword or identifier and the compiler cannot find it. Check out the exact line indicated, for a more detailed answer check out this thread.
stackoverflow.com/questions/25706216/what-does-a-cannot-find-symbol-or-cannot-resolve-symbol-error-mean

[@Firesealb99]

I had to use the -classpath modifier to include the folders that had the Classes in them.

[@MS-cn4dh]

Hi all.. I made it work later on.. will share soon if I remember what I did.. thanks to this tutorial for help!😊

[@brucergb]

@@Firesealb99 works for me, but additionally I download additional missing dependencies

[@ob0-china]

@@MS-cn4dh hey, could you share what you did please?

[@manjeetcscmahisaur4848]

Sir me java file me convart kar le raha hua lekin mai class file me nahi ho paa raha hai

[@walidpw9358]

please any one can help me with this error : javac acceuil.java
acceuil.java:3873: error: variable declaration not allowed here
boolean bool = (new File("Dossier_photos")).mkdirs();
^
1 error
all the fille are in the same folder, thank you

[@iteducator]

check if it's already declared

[@Tymek7123]

Im lost in the cmd, there is no in my this file name

[@iteducator]

what is not there in the cmd?

[@georgekoletsis3276]

Hello! At the step "Save all sources" the save process is taking too long and it is not finally successfully saved as zip. Could you help me please?

[@iteducator]

the time depends on the size of the file, if it is a large file try to extract and do it in parts, also make sure you have java installed properly. Check this video to see:
ruclips.net/video/i21CvFuDxek/видео.html
Are you getting any errors as well?

[@georgekoletsis3276]

@@iteducator Hello again, I use Java 11 for my project. It has been installed properly for sure. I have extracted in parts as you suggested and it is working for some classes. The size of my jar is 6.88MB. Let me know if you have any other solution in order to extract the whole jar! Many thanks again :)

[@vincentdevanc]

@@georgekoletsis3276 use jd 1.4.2 or older versions bro

[@itzmeee4]

I used versiom 1.4.2 and it soved mine

[@AqwsSuper]

The javac command brings me errors because some of the variables and functions in the .class file are being called by other parts of the .jar file, so anytime I try to use the javac command on the one specific .class file I made changes to, it'll come up with errors saying that certain functions and variables and symbols aren't defined/recognized (because they come from other parts of the .jar), this is the only part I'm having trouble in, is there any way to convert this .java file into a .class? I've been stuck on trying to do this last part for a while

[@iteducator]

you need to place all the dependencies packages and classes in the same paths as the java file in order to compile

[@AverageSchizo]

@@iteducator what does that even meannnn
what is a dependency package, you didn't cover that at all in the video?

[@iteducator]

@@AverageSchizo it's basic programming, and as the name suggests dependency, which means the package of code that your program is dependent on. In Java these are the imported packages in start of the code file.

[@Roz_ggez]

Bro did u get any solution? I got the same problem too

[@generalpashon]

@@Roz_ggez put the .java file in root of unpacked archive and call the javac command here

[@ペルマナの家族]

its work thankyou very much

[@iteducator]

You're welcome! Glad you found it helpful

[@naveenkumar1999]

Hey, I'm getting a package not found error while trying to compile using 'javac'. What should I do?

[@iteducator]

You must include it for it to compile

[@naveenkumar1999]

@@iteducator I have all those packages included.

[@iteducator]

stackoverflow.com/questions/3041543/package-not-found-javac
Try this

[@naveenkumar1999]

@@iteducator okay thanks, I'll try that

[@NguyenChang-qn8uz]

OMG thank you sir very muchhhh

[@iteducator]

Thanks

[@Aru8675]

Bro i don't understand anything clearly please make another video how to convert jar files into Java and then edit with the example of any game or app

[@iteducator]

Please watch it again, all the steps are there.

[@jurgenoerlemans1]

I had some difficulties too whwn I watched it the first time , but you have to really watch carefully. All steps are shown. I made some notes with pen and paper to 'educate myself :-) . It helps . .'

[@hambernat6444]

This tutorial is stupid, guy is clicking random stuff, swinging mouse right and left and doing things calling "these" in the same time moving mouse randomly...

[@mystic837]

When save all source . It run 50%. Why bro?

[@iteducator]

Is your file too large? if yes, then try it in parts by extracting

[@jurgenoerlemans1]

great explanation. But . . my issue is that when I want to compile the changed Java file, i get an error on the package name, which starts with
package WEB-INF.string1.string2.string3
It is the '-' between WEB and INF that is not allowed. However; I didn't invent the WEB-INF: It was already in the source file (which is a working application. Anybody any ideas?

[@iteducator]

Can you share the error you're getting, and have you placed the WEB-INF in the exact path

[@peony_si_ibrahimkayyis6050]

@@iteducator i also get the same error

[@mrakobes6888]

THAAAAANKS!

[@anulagrawal5300]

Will this work for EAR also ?

[@iteducator]

yes, it will.

[@埊]

what if my java file has 5 classes, 3 of which are needed to be edited[these are not taking much space in notepad], will the decompilation et compilation break anything?
and is the java file and executable jar file the same thing?

[@iteducator]

It won't cause an exception if there are no errors. JAR file and java file are different things.

[@user-hq4ep7ys2t]

how to install java compiler?

[@iteducator]

you have to install Java Development Kit (JDK) for windows

[@user-hq4ep7ys2t]

@@iteducator ik, its old java i already fixed

[@Valyk027]

Thanks

[@leno_tc_1]

thank you very much :)

[@7pro455]

My like is number @300@❤️❤️

[@PassaggioTecnologia]

top

[@worldnewsvideos]

❣👍👍👍👍👍👍👍👍👍

[@sureshkumar-pc7qo]

thank u very much :)

[@iteducator]

You're welcome!