iJava, an Experiment of Java Runtime on iOS done by Passionate Self-Taught Java developer with almost 3 years of experience in order to Reach niche goal.

We all know that Java never runs Natively on iOS since .class files from jar file is interpreted by JVM (Java Virtual Machine) which is absent on iOS, and JIT (Just in Time) Compilation is restricted.

But what I wanted to do is to run GUI-less Java code on my IPhone 5s (iOS 12.5.8, yes the version is old) to write a simple Experiment.txt file in documents folder.

At first, I tried to use Runtime translation tool such as J2ObjC (Which is developed by Google) and it used to convert GUI-Less .java files into .h ObjectiveC code which you had to add in your XCode Command line tool Project, But...I never had XCode or MacOS, No major Friends who could've helped or No place to borrow Mac from. I used to check J2ObjC's Github Repository, their official website yet There was no Windows-supported way. I even noticed Two versions of J2ObjC Eclipse plugins from Website (Like J2ObjC 1.7 or something) which was not even installable by today. I Moved into tools such as Codename One or GraalVM combined with Gluon Substrate (But None of them were working without Mac). Even Libraries like RoboVM didn't work much. I used to ask for help on Reddit iOS programming page to either get No Xcode users's attention or negative answers, I used to search for days in iOS programming discord servers but I didn't get precise help even if some attention was good. I tried to post in Facebook and everyone who reached out said No to help even if my Experiment was only about them using J2ObjC and XCode on their Mac.

But one day, I stumbled upon one nice website which lets you to convert GUI-less Java code into ObjectiveC code (with libraries! as long as they are minor), and guess how it unfold? I successfully converted my GUI-less Java code into ObjectiveC code and I saved it as .m file format. Since nobody was about to help, my Friend that I met months ago (Yes, the owner of iCodeWin), decide to try to convert my code.m file (the ObjectiveC code which I saved) and he got me some Unsigned IPA! which I signed by using 3uTools (yet it gave different failures and didn't sign new IPAs so later I used Sideloady which is very handy to directly install and sign IPAs on iOS), but iJava application on my IPhone 5 was working but it was crashing immediately and file writting wasn't working. In crash analysis, I found out that current IPA does not fall under arm64 architecture, so I had to ask my friend to set Deployment target and Architecture correctly (But he was using Xcodebuild happily but he wasn't able to set settings for IPA manually), so he reminded me about That Github repository that he send me days ago when he was bussy, so I forked it and started working with it (Luckily I got some instructions). And after many Github Action Errors and commits, I finally managed to build IPA with icon correctly. Finally after long dealing with Obstacles and failures, I managed to complete my goal of running Java on iOS 12.5.8, File is getting written flawlessly, and App no longer crashes. But I have to admit that XCode project was provided by One of the my friend iOS developer who usually worked with Swift but managed to send me valid ObjectiveC Project for XCode via Email which I Used for this Repository (this was critical part).

People's realitionship behind this project:

• Bacho Dev (Local Georgian iOS developer): Helped to provide XCode project

• ShadowX (Proud Owner of iCodeWin & iCodeSwift): Helped with this Github repository and Xcodebuild. Also see ShadowX's portfolio: https://shadowhex-biography.vercel.app/

• TopWorkNow (One of the Partners from that Company's worker who I found through Programming discord community, though their help was dedicated but limited). Big Thanks for everyone who supported me or Played role in this.

  Conclusion: Java Runtime by itself on iOS is very limited unless large work is involved, Java is never primary development language on iOS, it only works as niche experiment rather than something that you'd use to make Full-blown iOS app, Java on iOS can be used for small logical operations if converted to simple ObjectiveC code.