What if Java had Kotlin-style null-safety without migrating your Spring Boot project to Kotlin?

I've been building JADEx — a source-to-source compiler that adds two things Java has always been missing: null-safety and final-by-default semantics. No JVM changes, no runtime dependency, just safer Java. The problem If you've worked on a large Spring Boot codebase, you've seen this everywhere: public String getUsername(User user) { if (user == null) return null; if (user.getProfile() == null) return null; return user.getProfile().getUsername(); } The usual options: @NonNull / @Nullable annotations — opt-in, unenforced at the language level Migrate to Kotlin — cost-prohibitive for large, widely-used legacy Java codebases What JADEx does: Null-Safety JADEx introduces .jadex source files. Non-null is the default. Type? is the explicit opt-in for nullable. // UserService.jadex public String? getUsername(User? user) { return user?.profile?.username; } The ?. operator chains safely. The ?: Elvis operator provides a fallback: String? name = repository.findName(id); String display = name?.to