1. Let's consider "sumOfSquares += value*value" in code below. I think "value" should be converted to long in order to avoid overflow for big numbers.

    class IntSummaryStatistics {
        ...
        @Override
        public void accept(int value) {
            ++count;
            sum += value;
            sumOfSquares += value*value;
            min = Math.min(min, value);
            max = Math.max(max, value);
        }
    ...
    }

2. Typo: "max = Math.min(max, other.max);", please see code below. The same typo could also be seen in DoblueSummaryStatistics and LongSummaryStatistics.

    class IntSummaryStatistics {
    ...
        public void combine(IntSummaryStatistics other) {
            count += other.count;
            sum += other.sum;
            sumOfSquares += other.sumOfSquares;
            min = Math.min(min, other.min);
            max = Math.min(max, other.max);
        }
    ...
    }