code: public long size(String fileName) {
  		try {
  			IoChannel fileChannel = getFileChannel(fileName);
  			return fileChannel.size() / BLOCK_SIZE;
  		} catch (IOException e) {
  			throw new RuntimeException("cannot access " + fileName);
  		}
  	}
docs: Returns the number of blocks in the specified file.
  
  @param fileName
  the name of the file
  
  @return the number of blocks in the file