code: public int getIndex(String feature)
  	{
  		//logger.debug("FeatureIndex.get : " + feature + "(" + count + ")");
  		Integer index = (Integer) map.get(feature);
  
  		if (index == null)
  			return -1;
  
  		return index.intValue();
  	}
docs: Returns the <i>index</i> of the specified feature and adds
  the feature to the index if it is not present yet.
  
  @param feature	the feature.
  @return 			the <i>index</i> of the specified feature.