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Stanford Parser processes raw text in English, Chinese, German, Arabic, and French, and extracts constituency parse trees.

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package edu.stanford.nlp.trees;

import edu.stanford.nlp.process.Morphology;


/**
 * Stems the Words in a Tree using Morphology.
 *
 * @author Huy Nguyen ([email protected])
 */
public class WordStemmer implements TreeVisitor {

  public WordStemmer() { }

  @Override
  public void visitTree(Tree t) {
    // A single Morphology is not threadsafe, so to make this class
    // threadsafe, we have to create a new Morphology for each visit
    processTree(t, null, new Morphology());
  }

  private static void processTree(Tree t, String tag, Morphology morpha) {
    if (t.isPreTerminal()) {
      tag = t.label().value();
    }
    if (t.isLeaf()) {
      t.label().setValue(morpha.lemma(t.label().value(), tag));
    } else {
      for (Tree kid : t.children()) {
        processTree(kid, tag, morpha);
      }
    }
  }

  /**
   * Reads, stems, and prints the trees in the file.
   *
   * @param args Usage: WordStemmer file
   */
  public static void main(String[] args) {
    Treebank treebank = new DiskTreebank();
    treebank.loadPath(args[0]);
    WordStemmer ls = new WordStemmer();
    for (Tree tree : treebank) {
      ls.visitTree(tree);
      System.out.println(tree);
    }
  }

}