alt Hacker News> More generally than just Java, nullability is often a property not of a type but of a variable.
This is a tangent, but I'm not sure I follow this. Can you give an example to make this clear?
> More generally than just Java, nullability is often a property not of a type but of a variable.
This is a tangent, but I'm not sure I follow this. Can you give an example to make this clear?
Yes, but it comes from Java having both runtime and compile-time types; it's harder to make the distinction in languages that don't have runtime types.
In Java, you can ask, `x instanceof T` (and this is a runtime test), which means, is x one of the values in the set of values allowed by T. `null instanceof Integer` is false, even though a variable of type `Integer` can be assigned a null. So you can think of `Integer x` as being `Integer|null x`, i.e. x can hold a null, even though `null instancof Integer` is false.