in mail-archive/stats/src/main/java/org/apache/sling/mailarchive/stats/impl/MailStatsProcessorImpl.java [146:157]
private void addRecord(Date d, String from, String to) {
final DataRecord r = new DataRecord(d, to);
synchronized (data) {
final DataRecord existing = data.get(r.getKey());
if(existing == null) {
r.increment(from);
data.put(r.getKey(), r);
} else {
existing.increment(from);
}
}
}