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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.process;


import edu.stanford.nlp.io.Lexer;
import edu.stanford.nlp.io.RuntimeIOException;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.Reader;


/**
 * An implementation of {@link Tokenizer} designed to work with
 * {@link Lexer} implementing classes.  Throw in a {@link Lexer} on
 * construction and you get a {@link Tokenizer}.
 *
 * @author Roger Levy
 */
public class LexerTokenizer extends AbstractTokenizer {

  private Lexer lexer;

  /**
   * Internally fetches the next token.
   *
   * @return the next token in the token stream, or null if none exists.
   */
  @Override
  protected String getNext() {
    String token = null;
    try {
      int a = Lexer.IGNORE;
      while ((a = lexer.yylex()) == Lexer.IGNORE) {
        ; // skip tokens to be ignored
      }
      if (a == lexer.getYYEOF()) {
        token = null;
      } else {
        token = lexer.yytext();
      }
    } catch (IOException e) {
      // do nothing, return null
    }
    return token;
  }

  /* Constructs a tokenizer from a {@link Lexer}
   */
  public LexerTokenizer(Lexer l) {
    if (l == null) {
      throw new IllegalArgumentException("You can't make a Tokenizer out of a null Lexer!");
    } else {
      this.lexer = l;
    }
  }

  /* Constructs a tokenizer from a {@link Lexer} and makes a {@link
   * Reader} the active input stream for the tokenizer.
   */
  public LexerTokenizer(Lexer l, Reader r) {
    this(l);

    try {
      l.yyreset(r);
    } catch (IOException e) {
      throw new RuntimeIOException(e.getMessage());
    }

    getNext();
  }


  /**
   * for testing only
   */
  public static void main(String[] args) throws IOException {
    Tokenizer t = new LexerTokenizer(new JFlexDummyLexer((Reader) null), new BufferedReader(new FileReader(args[0])));
    while (t.hasNext()) {
      System.out.println("token " + t.next());
    }
  }

}