docs: public void loadDirectory( String lexDir ) throws IOException
      {
          File path = new File(lexDir);
          if ( ! path.exists() ) {
              throw new IOException("Lexicon directory ["+lexDir+"] does'n exists.");
          }
          
          /*
           * load all the lexicon file under the lexicon path 
           *     that start with "lex-" and end with ".lex".
           */
          File[] files = path.listFiles(new FilenameFilter(){
              @Override
              public boolean accept(File dir, String name) {
                  return (name.startsWith("lex-") && name.endsWith(".lex"));
              }
          });
          
          for ( File file : files ) {
              load(file);
          }
      }