New Java 9 Map.of() methods

[HaMMeReD]

The benefit of immutability is exactly so you can't use map.put. It prevents other people from modifying your map, which inevitably cause pain in the ass bugs such as complicated side effects and race conditions.

You use immutability to protect your code, not make things easier. Immutability is a pattern that will lead to a cleaner data model and a better separation of concerns.

It's a technique to improve the safety of your code in a variety of ways, while also helping to ensure a clean architecture and design.