Collectors.LongStatistics Min/Max Values

[Paul Sandoz]

On Feb 28, 2013, at 11:49 PM, Niels Nonsense <niels.nwx at gmail.com> wrote:

> The accept method of LongStatistics should be rewritten as:
> @Override
> public void accept(long value) {
>    sum += value;
>    min = count == 0 ? value : Math.min(min, value);
>    max = Math.max(max, value);
>    ++count;
> }
> Similar for combine and the other primitives.
> 

A simpler approach is to initialize min to Long.MAX_VALUE and max to Long.MIN_VALUE and the min/max methods should return OptionalLong:

        public OptionalLong getMin() {
            return count > 0 ? OptionalLong.of(min) : OptionalLong.empty();
        }

to be consistent with the stream min/max methods.

For DoubleStatistics i think the initial min and max values can be Double.POSITIVE_INFINITY and Double.NEGATIVE_INFINITY respectively. We should also think about what it means if a NaN is present. We could state the behaviour uses the same rules as Math.min/max, which means if a Nan is present then NaN will be returned.

Paul.

> 2013/2/28 Robert J. Saulnier <robert.j.saulnier at gmail.com>
> 
>> I'm guessing this was already discussed.
>> 
>> Why does the following print "min=0" instead of "min=1"?
>> 
>> List<Long> nums = Arrays.asList(1L, 2L, 3L);
>> 
>> Collectors.LongStatistics stats =
>> nums.stream().collect(Collectors.toLongStatistics());
>> 
>> System.out.println("min=" + stats.getMin());
>> 
>> Same issue with max if all the numbers are negative.
>> 
>> 
>