OP mentioned one of the other approaches..."Optional". An `Optional<String>` will be a non-null reference to either a present value, or an absent value. It's really just modelling null at a non-syntax level, and encourages checking whether there is a value explicitly (i.e. it's self documenting that you need to check if the value is present before using it).

Proponents of Optional will then say that every non-Optional reference must never be null, through static/runtime assertions (like @Nonnull, checkNotNull(), etc)