code: private boolean readNullValueAtRowCol( int currentfilerow, int currentfilecol ) throws IOException {
          /*
           * If the null file doesn't exist and the map is an integer, than it is an old integer-map
           * format, where the novalues are the cells that contain the values 0
           */
          if (nullFile != null) {
              long byteperrow = (long) Math.ceil(fileWindow.getCols() / 8.0); // in the
              // null
              // map of
              // cell_misc
              long currentByte = (long) Math.ceil((currentfilecol + 1) / 8.0); // in the
              // null
              // map
  
              // currentfilerow starts from 0, so it is the row before the one we
              // need
              long byteToRead = (byteperrow * currentfilerow) + currentByte;
  
              nullFile.seek(byteToRead - 1);
  
              int bitposition = (currentfilecol) % 8;
  
              byte[] thetmp = new byte[1];
              thetmp[0] = nullFile.readByte();
              BitSet tmp = FileUtilities.fromByteArray(thetmp);
  
              boolean theBit = tmp.get(7 - bitposition);
              /*
               * if (theBit) { System.out.println("1 at position: " + (7-bitposition) + " due to
               * bitposition: " + bitposition); } else { System.out.println("0 at position: " +
               * (7-bitposition) + " due to bitposition: " + bitposition); }
               */
              return theBit;
  
          }
          // else
          // {
          // /* There is no null file around */
          // if (rasterMapType > 0)
          // {
          // // isOldIntegerMap = true;
          // return false;
          // }
          // else
          // {
          // //throw some exception
          // return false;
          // }
          //
          // }
          return false;
  
      }
docs: read the null value from the null file (if it exists) and returns the information about the
  particular cell (true if it is novalue, false if it is not a novalue
  
  @param currentfilerow
  @param currentfilecol
  @return