code: import java.util.List;
  
  import edu.stanford.nlp.ling.Label;
  import edu.stanford.nlp.trees.Tree;
  import edu.stanford.nlp.trees.TreeTransformer;
  import edu.stanford.nlp.util.Generics;
  
  /**
   * This transformer collapses chains of unary nodes so that the top
   * node is the only node left.  The Sentiment model does not handle
   * unary nodes, so this simplifies them to make a binary tree consist
   * entirely of binary nodes and preterminals.  A new tree with new
   * nodes and labels is returned; the original tree is unchanged.
   *
   * @author John Bauer
   */
  public class CollapseUnaryTransformer implements TreeTransformer {
    public Tree transformTree(Tree tree) {
      if (tree.isPreTerminal() || tree.isLeaf()) {
        return tree.deepCopy();
      }
  
      Label label = tree.label().labelFactory().newLabel(tree.label());
      Tree[] children = tree.children();
      while (children.length == 1 && !children[0].isLeaf()) {
        children = children[0].children();
      }
      List<Tree> processedChildren = Generics.newArrayList();
      for (Tree child : children) {
        processedChildren.add(transformTree(child));
      }
      return tree.treeFactory().newTreeNode(label, processedChildren);
    }
  }
  