if(val == null) { it.remove(); continue; }
        public void run() {            Map.Entry entry;            Object key;            Long val;            if(trace)                log.trace("checking for expired senders, table is:\n" + printTimeStamps());            long current_time=System.currentTimeMillis(), diff;            for(Iterator it=timestamps.entrySet().iterator(); it.hasNext();) {                entry=(Map.Entry)it.next();                key=entry.getKey();                val=(Long)entry.getValue();                diff=current_time - val.longValue();                if(diff > timeout) {                    if(trace)                        log.trace("haven't received a heartbeat from " + key + " for " + diff + " ms, suspecting it");                    suspect((Address)key);                }            }        }