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Cake day: November 6th, 2025

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  • t’s true that JPlus holds a similar position to TypeScript. However, it is a programming language. Here’s a definition quoted from the main page of the TypeScript website -> “TypeScript is a strongly typed programming language that builds on JavaScript, giving you better tooling at any scale.”

    Similarly,

    JPlus is a Java superset programming language — fully compatible with Java, offering modern language features like null safety, boilerplate code generation, and other enhancements to reduce developer burden and maximize productivity.




  • The C Preprocessor also does all of those things. That’s expected of a preprocessor. If you say “you can write java code with a bit of extra sugar and JPlus turns it back into ‘regular’ java,” then that’s a preprocessor.

    A simple preprocessor only performs code transformation and cannot analyze the meaning of the code or ensure type safety. However, JPlus goes beyond mere transformation by providing static analysis capabilities, such as generating a parse tree and checking nullability. It also includes functionality to automatically generate necessary Java code through the apply syntax. As a result, the combination of performing nullability static analysis and generating code via apply cannot be expressed or handled using any existing Java syntax alone.


  • JPlus follows standard Java syntax while aiming to be an “Upgraded Java” by adding features that Java developers consider practically useful in real-world projects. This allows existing Java developers to utilize new features with minimal learning curve. All features are added on top of Java syntax. For example, null-safety syntax (type?, ?.) and boilerplate code generation syntax (apply). As a result, developers can experience an enhanced version of Java while continuing to use existing Java code and libraries without modification. This should clarify exactly where JPlus fits in the ecosystem.


  • Thank you for the excellent question.

    1. How does JPlus handle null safety in Java library interfaces?

    • JPlus is currently implemented at the MVP level. Therefore, all Java library interfaces are treated as non-null by default. As a result, developers need to manually check for nullability when interacting with Java libraries.

    • When referencing Java library objects, always declare the variables as nullable (type?) and use the null-safe operator (?.) when accessing them to prevent null pointer exceptions (NPEs).

    • In future implementations, we plan to leverage nullability annotations in Java library code to add null-checking logic. However, since not all Java libraries include such annotations, developers will still need to manually handle null checks. The same applies to Kotlin: platform types are used, so developers are responsible for performing null checks.


    2. If nullability information is a type metadata extension for compile-time checking, does that inevitably break on library interfaces when I create both library and consuming app with JPlus?

    • In the current JPlus MVP, when converting to Java code, nullability information specified in the JPlus files is not converted into @Nullable/@Nonnull annotations.

    • Therefore, using static analysis tools that rely on these annotations may cause issues at compile time.

    • This feature will be supported in the next version, which will include conversion to @Nullable/@Nonnull. Thank you for your valuable feedback.


    Finally, for faster responses, please post any future questions on the JPlus GitHub Discussions page: https://github.com/nieuwmijnleven/JPlus/discussions.









  • You can probably adopt both for a large existing project. Old files get compiled with JPlus, new files will be written in Kotlin. Old files can also gradually be ported to kotlin.

    Exactly, that could work. You can keep the existing files as they are and compile them with JPlus, while writing new modules in Kotlin to adopt it gradually. JPlus can serve as a stepping stone before moving fully to Kotlin. However, converting all Java code in an existing project to Kotlin would not only carry significant risks but also be costly. With JPlus, you can fully leverage the proven existing Java codes.








  • AFAIK Kotlin and Java code can co-exist as source level. Never tried it though. I guess it depends on the end case scenario what to use.

    JPlus retains almost all of Java’s syntax while providing conveniences like null checks, allowing Java developers to use it immediately without additional learning. In contrast, Kotlin can utilize Java classes but requires learning Kotlin syntax and its libraries, and it cannot use Java syntax directly or automatically guarantee null safety. Therefore, JPlus offers a distinct advantage over Kotlin.