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Stanford CoreNLP provides a set of natural language analysis tools which can take raw English language text input and give the base forms of words, their parts of speech, whether they are names of companies, people, etc., normalize dates, times, and numeric quantities, mark up the structure of sentences in terms of phrases and word dependencies, and indicate which noun phrases refer to the same entities. It provides the foundational building blocks for higher level text understanding applications.

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package edu.stanford.nlp.ling;

import edu.stanford.nlp.process.Morphology;

/**
 *
 * A {@code WordLemmaTagFactory} acts as a factory for creating
 * objects of class {@code WordLemmaTag}.
 *
 * @author Marie-Catherine de Marneffe
 */
public class WordLemmaTagFactory implements LabelFactory {

  public static final int LEMMA_LABEL = 1;
  public static final int TAG_LABEL = 2;

  private final char divider;


  /**
   * Create a new {@code WordLemmaTagFactory}.
   * The divider will be taken as '/'.
   */
  public WordLemmaTagFactory() {
    this('/');
  }


  /**
   * Create a new {@code WordLemmaTagFactory}.
   *
   * @param divider This character will be used in calls to the one
   *                argument version of {@code newLabel()}, to divide
   *                word from lemma and tag.
   */
  public WordLemmaTagFactory(char divider) {
    this.divider = divider;
  }


  /**
   * Make a new label with this {@code String} as the value (word).
   * Any other fields of the label would normally be null.
   *
   * @param labelStr The String that will be used for value
   * @return The new WordLemmaTag (lemma and tag will be {@code null})
   */
  @Override
  public Label newLabel(String labelStr) {
    return new WordLemmaTag(labelStr);
  }


  /**
   * Make a new label with this {@code String} as a value component.
   * Any other fields of the label would normally be null.
   *
   * @param labelStr The String that will be used for value
   * @param options  what to make (use labelStr as word, lemma or tag)
   * @return The new WordLemmaTag (word or lemma or tag will be {@code null})
   */
  @Override
  public Label newLabel(String labelStr, int options) {
    if (options == TAG_LABEL) {
      return new WordLemmaTag(null, null, labelStr);
    } else if (options == LEMMA_LABEL) {
      return new WordLemmaTag(null, labelStr, null);
    } else {
      return new WordLemmaTag(labelStr);
    }

  }


  /**
   * Create a new word, where the label is formed from
   * the {@code String} passed in.  The String is divided according
   * to the divider character.  We assume that we can always just
   * divide on the rightmost divider character, rather than trying to
   * parse up escape sequences.  If the divider character isn't found
   * in the word, then the whole string becomes the word, and lemma and tag
   * are {@code null}.
   * We assume that if only one divider character is found, word and tag are presents in
   * the String, and lemma will be computed.
   *
   * @param labelStr The word that will go into the {@code Word}
   * @return The new WordLemmaTag
   */
  @Override
  public Label newLabelFromString(String labelStr) {
    int first = labelStr.indexOf(divider);
    int second = labelStr.lastIndexOf(divider);
    if (first == second) {
      return new WordLemmaTag(labelStr.substring(0, first), Morphology.lemmaStatic(labelStr.substring(0, first), labelStr.substring(first + 1)), labelStr.substring(first + 1));
    } else if (first >= 0) {
      return new WordLemmaTag(labelStr.substring(0, first), labelStr.substring(first + 1, second), labelStr.substring(second + 1));
    } else {
      return new WordLemmaTag(labelStr);
    }
  }


  /**
   * Create a new {@code WordLemmaTag Label}, where the label is
   * formed from the {@code Label} object passed in.  Depending on what fields
   * each label has, other things will be {@code null}.
   *
   * @param oldLabel The Label that the new label is being created from
   * @return a new label of a particular type
   */
  @Override
  public Label newLabel(Label oldLabel) {
    return new WordLemmaTag(oldLabel);
  }

}