String ac = areaCode;
String ac = StringUtils.defaultString(areaCode);
    List<DialPattern> calculateDialPatterns(String areaCode) {        String ac = areaCode;        int acLen = areaCode.length();        int variableLen = -1;        if (m_externalLen > 0) {            // someone specified external len - try to calculate variable len            variableLen = m_externalLen - acLen;            if (variableLen < 0) {                // area code is longer than external lenght - need to cut it                variableLen = 0;                ac = areaCode.substring(0, m_externalLen);            }        }        List<DialPattern> patterns = new ArrayList<DialPattern>(4);        if (StringUtils.isNotBlank(m_pstnPrefix) && StringUtils.isNotBlank(m_longDistancePrefix)) {            String prefix = m_pstnPrefix + m_longDistancePrefix + ac;            patterns.add(new DialPattern(prefix, variableLen));        }        if (m_pstnPrefixOptional && StringUtils.isNotBlank(m_longDistancePrefix)) {            String prefix = m_longDistancePrefix + ac;            patterns.add(new DialPattern(prefix, variableLen));        }        if (StringUtils.isNotBlank(m_pstnPrefix) && m_longDistancePrefixOptional) {            String prefix = m_pstnPrefix + ac;            patterns.add(new DialPattern(prefix, variableLen));        }        if (m_pstnPrefixOptional && m_longDistancePrefixOptional) {            patterns.add(new DialPattern(ac, variableLen));        }        return patterns;    }