[threeten-dev] [threeten-develop] Rough draft of TemporalAmount

[Douglas Surber]

The JavaDoc for Period.getUnit says it returns a Set, not a List.

Douglas

At 11:10 AM 1/26/2013, Roger Riggs wrote:
>Hi,
>
>Some revisions and comments inline:
>
>javadoc:
>    http://cr.openjdk.java.net/~rriggs/javadoc-temporalamount/
>
>webrev:
>    http://cr.openjdk.java.net/~rriggs/webrev-temporalamount/
>
>On 1/25/2013 10:54 AM, Stephen Colebourne wrote:
> > On 25 January 2013 15:21, Roger 
> Riggs<Roger.Riggs at oracle.com>  wrote:
> >> So, the simplest option is
> >> Duration = SECONDS + NANOS
> >> Period + YEARS + MONTHS + DAYS + NANOS
> >>
> >> The javadoc for Period describes itself has supporting the most 
> commonly
> >> used units
> >> including "time units with an exact duration".  To be consistent 
> get(unit)
> >> should follow
> >> that pattern.
> > I think that we need to require that the combination of 
> getUnits() and
> > get() returns the complete state of the object.
> >
> > A Period is an amount, created by adding the total of years, 
> months
> > days and time (in nanos). A user querying the period should be 
> able to
> > get the total "amount". If hours/minutes/seconds are supported, 
> then
> > get(HOURS)+get(MINUTES)+get(SECONDS)+get(NANOS) should be the 
> total
> > amount, and all other units would be an error.
>right
> >
> > The alternate model for the interface is that it is just a 
> "friendly"
> > get, like Temporal, that returns as much as it can. But we don't 
> have
> > the rest of the infrastructure to do that in terms of converting 
> a
> > user type of HALF_YEARS from the provided type of YEARS.
>All Units have a Duration, sometimes estimated that can be used for
>conversions
>if deemed necessary.
> >
> > Given that there are multiple choices this gets tricky.
> >
> > (I note again that adding this interface is risky because we 
> don't
> > have the use cases to validate it. Adder and Subtractor are safe 
> and
> > cannot be wrong. This interface may well not be what we really 
> need,
> > forcing a TemporalAmount2 in the future)
> >
> > I would say that these models:
> >   Period = YEARS + MONTHS + DAYS + NANOS
> >   Period = YEARS + MONTHS + DAYS + HOURS + MINUTES(excluding 
> hours) +
> > SECONDS(excl hr/min) + NANOS(excl hr/min/sec)
> > provides sufficient data for later default interface methods. 
> (ie.
> > where only the above units can be queried.) The former is a more
> > accurate representation of the state of the class and easier for
> > framework code to work with. The latter is more designed for 
> human
> > code.
>Period is defined to be the 7 values that make up the amount and 
>with
>the Units and Durations the caller can convert to any desired Unit.
> >
> > The choice of providing a general conversion mechanism using 
> durations
> > in get(Unit) may be nice for users, but it would be 
> non-extensible in
> > future JDKs (default interface methods would have insufficient
> > information to work with).
>The methods getUnits and get(unit) provide a complete picture of the 
>
>TemporalAmount
>(as long as there is no overlap between the units) any caller can
>iterate over the
>supported Units and get the total value.
>
>And the missing information is?
>
>For example, the default method for addTo(Temporal) might be:
>      Temporal plus(Temporal t) {
>          Temporal accum = t;
>           for (TemporalUnit unit: this.getUnits()) {
>               long v = this.get(unit);
>               if (v != 0) {
>                   accum = accum.plus(v, unit);
>               }
>          }
>          return accum;
>       }
>
>Changing getUnits to return List<TemporalUnit> and returning them
>in decreasing duration will allow predicable use and results.
> >
> >
> > Given all this, I think  Period = YEARS + MONTHS + DAYS + NANOS 
> is the
> > simplest model. But since its not very user friendly, it may be 
> best
> > to return it as a Map<Unit,Long>, or to rename get(Unit) to 
> something
> > less attractive.
>The TemporalAmount is already effectively a Map<Unit, Long>.
>
>Roger
>
>
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