I'm aware that Groovy now supports optional typing but if I'm going this path, I prefer to switch to Kotlin, which I describe as "Java with everything that's bad removed".
If that's what you want wouldn't Ceylon be a better choice? If you're still using the Java standard library you still have the billion dollar mistake (null) everywhere.
I see it as "Java without types", myself.
I'm aware that Groovy now supports optional typing but if I'm going this path, I prefer to switch to Kotlin, which I describe as "Java with everything that's bad removed".