private final void print2( Object[] kvs) {
    for( int i=0; i<len(kvs); i++ ) {
      Object key = key(kvs,i);
      Object val = val(kvs,i);
      Object U = Prime.unbox(val);
      if( key != null && key != TOMBSTONE &&  // key is sane
          val != null && U   != TOMBSTONE ) { // val is sane
        String p = (val==U) ? "" : "prime_";
        System.out.println(""+i+" ("+key+","+p+val+")");
      }
    }
    Object[] newkvs = chm(kvs)._newkvs; // New table, if any
    if( newkvs != null ) {
      System.out.println("----");
      print2(newkvs);
    }
  }