Default value for date/time (original) (raw)

Stephen Colebourne scolebourne at joda.org
Wed May 9 00:37:35 UTC 2018

On 9 May 2018 at 01:13, John Rose <john.r.rose at oracle.com> wrote:

I worry that while the key principle has got the project a long way, it is too hard line when it comes to some potential value types - Currency or Money being other examples where a default is silly, but they are otherwise fully value-like. Any value type measuring a scaled amount is going to have a zero right? That's the default, probably. It's affine amounts like times that don't have a good default.

Whats the default Currency? USD is a not an acceptable answer. Money is the same as it can't exist without a currency.

What about a Distance object? Is it measured in Miles or Kilometers by default?

class ObserveTheDefault { LocalDateValue x; LocalDateValue[] a = new LocalDateValue[1]; void test() { System.out.println(x); assert(LocalDateValue.default.equals(x)); System.out.println(a[0]); assert(LocalDateValue.default.equals(a[0])); } public static void main(String… av) { new ObserveTheDefault().test(); } }

My suggestion was that code does not compile as LocalDateValue x wasn't assigned in the constructor (not "works like an int", but then its not like an int). Anything else risks allowing a "null-like" LocalDate to escape and head off causing havoc to real code - just like null does...

Anyway, I'm not expecting firm/final answers right now - value types has too far to go. Consider my points to be concerns that might be worth considering.

thanks Stephen

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