public void writeStringList(DataOutput out, List<String> stringList) throws IOException {
        strategy.writeStringList(out, stringList);
    }
Writes a List of Strings. This method handles the case when the List is
{@code null}.

@param out        the output stream.
@param stringList the List of Strings.
@throws IOException if an error occurs.
xmppserver/src/main/java/org/jivesoftware/util/cache/ExternalizableUtil.java