code: private void createNodes(DefaultMutableTreeNode top) {
  
      // categories
      DefaultMutableTreeNode category = null;
      // leaves
      DefaultMutableTreeNode defaultMutableTreeNode = null;
  
      // Wav Files
      category = new DefaultMutableTreeNode("Wav Files");
      top.add(category);
  
      long count = HJABirdsongDAO.selectCount();
      for (int i = 1; i <= count; i++) {
        HJABirdSong hJABirdsong = HJABirdsongDAO.selectSingle(i);
        hJABirdsong.getWavfilename();
        defaultMutableTreeNode = new DefaultMutableTreeNode(hJABirdsong);
        category.add(defaultMutableTreeNode);
      }
    }
docs: Create the tree
  
  @param top