import edu.stanford.nlp.trees.CollinsHeadFinder; //导入依赖的package包/类
/**
 * Syntactic complexity as defined by Lin (1996).
 * 
 * @param tree
 * @return
 */
private static int complexityOf(Tree tree) {
  tree.indexLeaves();
  tree.percolateHeads(new CollinsHeadFinder());
  tree.percolateHeadIndices();
  
  Set<Dependency<Label,Label,Object>> deps = tree.dependencies();
  int complexity = 0;
  for (Dependency<Label,Label,Object> dep : deps) {
    if (!(dep instanceof UnnamedConcreteDependency)) {
      throw new RuntimeException("Cannot measure syntactic complexity.");
    }
    UnnamedConcreteDependency uDep = (UnnamedConcreteDependency) dep;
    int headIndex = uDep.getGovernorIndex();
    int depIndex = uDep.getDependentIndex();
    complexity += Math.abs(headIndex - depIndex);
  }
  
  return complexity;
}