code: public void write(Writer out) throws IOException
  	{
  		//logger.debug("writing feature index");
  
  		PrintWriter pw = new PrintWriter(out);
  
  		Iterator it = map.entrySet().iterator();
  		//logger.debug("index size " + map.entrySet().size());
  
  		while (it.hasNext())
  		{
  			Map.Entry me = (Map.Entry) it.next();
  			// feature index
  			pw.println(me.getValue() + "\t" + me.getKey());
  		}
  		pw.flush();
  		pw.close();
  
  	}
docs: Writes the feature index into the specified
  output stream in a format suitable for loading
  into a <code>Map</code> using the
  {@link #read(Reader) write} method.
  
  @param out						a <code>Writer</code> object to
  provide the underlying stream.
  @throws IOException	if writing this feature index
  to the specified  output stream
  throws an <code>IOException</code>.