presto-spi/src/main/java/io/prestosql/spi/type/Decimals.java/Decimals/getMatcherGroup
class Decimals:    private static String getMatcherGroup(Matcher matcher, int group)
    {
        String groupValue = matcher.group(group);
        if (groupValue == null) {
            groupValue = "";
        }
        return groupValue;
    }