presto-main/src/main/java/io/prestosql/operator/aggregation/NumericHistogram.java/NumericHistogram/concat
class NumericHistogram:    private static void concat(double[] target, double[] first, int firstLength, double[] second, int secondLength)
    {
        System.arraycopy(first, 0, target, 0, firstLength);
        System.arraycopy(second, 0, target, firstLength, secondLength);
    }