Welcome. You've been writing AbstractSingletonProxyFactoryBean and we won't judge you — the ecosystem made you do it. But it's time. F# is what Java always wished it could be: expressive, type-safe, concise, and running on a genuinely great runtime (.NET, not JVM — yes, the GC is better).
Pain you're leaving behind: 10 files for one feature, XML everywhere, Spring Boot startup time, Optional<Optional<List<? extends Comparable<? super T>>>>, and NullPointerException at line 1 of your stack trace.
What you'll love immediately:
- A
Personrecord is one line. Getters, equals, hashCode, toString — free. - Pattern matching on sealed types, with exhaustiveness checking — the Java 21 feature, but good
- No
Optional.ofNullable(x).map(f).orElse(null)—Option<'T>is a language citizen - Build time:
dotnet buildis fast. SageFs day-to-day: no build at all.
→ Start here: samples/from-java/hello.fsx
// Java: public record Person(String name, int age) {} + equals + hashCode + toString
// F#:
type Person = { Name: string; Age: int }
// structural equality: { Name = "Alice"; Age = 30 } = { Name = "Alice"; Age = 30 } → true
// toString: printfn "%A" { Name = "Alice"; Age = 30 } → { Name = "Alice"; Age = 30 }
// No Lombok. No Jackson annotations. Just data.