[alzoid]

Java introduced Optional to remove nulls. It also introduced a bunch of things to make it behave like functional languages. You can use records for immutable data, sealed interfaces for domain states, you can switch on the sealed interface for pattern matching, use the sealed interfaces + consumers or a command pattern to remove exception handling and have errors as values.

[tpoacher]

using an instance of a sealed class in a switch expression also has the nice property that the compiler will produce an error if the cases are incomplete (and as such there's also no need for a default case). So a good case for the "make invalid states unrepresentable" argument.