@Override
    public void characters(char[] ch, int start, int length) throws SAXException {
        try {
            String text = new String(Arrays.copyOfRange(ch, start, start + length));
            stringBuilder.append(text);
            super.characters(ch, start, length);
        } catch (SAXException e) {
            handleException(e);
        }
    }
The characters method is called whenever a Parser wants to pass raw...
characters to the ContentHandler. But, sometimes, phone numbers are split
accross different calls to characters, depending on the specific Parser
used. So, we simply add all characters to a StringBuilder and analyze it
once the document is finished.
tika-core/src/main/java/org/apache/tika/sax/PhoneExtractingContentHandler.java