private int nullSafeCompare(String first, String second) {
        int result = nullCompare(first, second);
        return result == NON_NULLS ? StringUtils.compare(first, second) : result;
    }
Compares the two given strings for order, handling null as necessary.

@return a negative integer, zero, or a positive integer as the first
        object is less than, equal to, or greater than the second object.
aws-java-sdk-cloudwatchmetrics/src/main/java/com/amazonaws/metrics/internal/cloudwatch/DimensionComparator.java