Cleanest way to format a String
<p>I'm trying to format a phone number which is stored without formatting in a database.
Now currently I just use substring and String concatination to form the formatted String but I'm looking for a cleaner/faster/less memory intensive method. (and I don't mean just using a StringBuilder).</p>

<p>I looked at String.format but that only takes a list of parameters (as in ...) and not a chararray.</p>
