@Override public void exportTree(Tree tree) throws IOException {
  java.util.List<Tree> trees=new ArrayList<Tree>();
  trees.add(tree);
  exportTrees(trees);
}

@ Override public void exportTree ( Tree tree ) throws IOException { java . util . List < Tree > trees = new ArrayList < Tree > ( ) ; trees . add ( tree ) ; exportTrees ( trees ) ; }
export a single tree
