public void printVisit( Tree.Node<String> node, int depth ) {
      
      for ( int i = 0; i < depth; ++i ) {
         System.out.print("-");
      }
      System.out.println( node.getData() );
      
      List<Tree.Node<String>> children = node.getChildren();
      
      for( int i = 0; i < children.size(); ++i ) {
         printVisit( children.get(i), depth+1 );
      }
   }