for(Enumeration e=sent_msgs.keys(); e.hasMoreElements();) sb.append(e.nextElement() + " ");
Set s=sent_msgs.keySet(); Long min_seqno=null, max_seqno=null; if(s != null) { min_seqno=(Long)Collections.min(s); max_seqno=(Long)Collections.max(s); } sb.append("[").append(min_seqno).append(" - ").append(max_seqno).append("]");
    String printSentMsgs() {        StringBuffer sb=new StringBuffer();        for(Enumeration e=sent_msgs.keys(); e.hasMoreElements();)            sb.append(e.nextElement() + " ");        return sb.toString();    }