public long highSeqnoSeenAt(Address sender) { long ret=-1; int index;  if(sender == null) return ret; index=getIndex(sender); if(index == -1) return ret; else
public long highSeqnoSeenAt(int index) { if(index < size())
    public long highSeqnoSeenAt(Address sender) {        long ret=-1;        int index;        if(sender == null) return ret;        index=getIndex(sender);        if(index == -1)            return ret;        else            return high_seqnos_seen[index];    }