OpenJDK Mobile is concerned with providing same APIs in the OpenJDK source repository to iOS and Android, albeit with more focus on iOS for its lack of traditional support for Java, given that Apple disallows the Java Virtual Machine (JVM) from running on the iOS platform.
Now, there is a proposal within the OpenJDK community seeking to jumpstart Java on iOS, which will result to restarting work on the OpenJDK Mobile project, with the new plan entailing the use of the GraalVM ahead-of-time (AOT) compilation for code at build time, even as just-in-time compilation is never an option for iOS.
This procedure has already been successfully used on Java 11, so employing OpenJDK classes and the GraalVM Native Images, Java developers will be able to create applications that run within the Apple rules.
Though, Java was used for Android development from the very beginning, but now Android is currently not Java 11-compliant and requires Android Studio, if it must be run, which procedures many developers find as tedious in using Java projects and libraries on Android. As such, the plan will also include a synchronized fork of OpenJDK master, using Project Skara.
The Skara-based repository would be employed in the building of the OpenJDK Mobile for iOS and Android; thus Java developers wouldn't have to learn Objective-C or Swift to write their software for the iOS platform.
And the fact that Java is cross-platform compliant, with security as a key cornerstone, it allows for secure connectivity with cloud services, makes it a big deal for mobile development.