In Kotlin, how does GSON.fromJson(…) manage to mutate a read-only field of an existing object?

In Kotlin, how can an instance’s read-only val field be mutated? In the following Kotlin code, gson.fromJson(…) gets a Thing(0) from the InstanceCreator and somehow manages to mutate value from 0 to …

How close possibility to add new data in H2?

I have a problem. After adding some data to database, I need to set read-only mode for whole DB. What is the easiest way to do that using h2 embedded DB with driver manager (jdbc)? Class.forName(“…