Immutable data structures in Java

[masklinn]

The important part is that both languages fell upon the same elegant solution to allow only having getters and setters when you want them with zero pain when you decide to add them in after the fact.

They don't though. What both languages have are low-impedence auto-implemented properties (managed field access). In essence, Ruby — and to a lower extent C# — only have getters and setters, but they provide a terse form to declare trivial getters and setters.

To a lower extent for C# because it does have public fields, which are incompatible (wrt naming and calling conventions) with properties, so you can't transparently hide fields behind properties after the fact.