src/java/org/apache/lucene/analysis/LetterTokenizer.java

package org.apache.lucene.analysis;

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import java.io.Reader;

/** A LetterTokenizer is a tokenizer that divides text at non-letters.  That's
  to say, it defines tokens as maximal strings of adjacent letters, as defined
  by java.lang.Character.isLetter() predicate.

  Note: this does a decent job for most European languages, but does a terrible
  job for some Asian languages, where words are not separated by spaces. */

public class LetterTokenizer extends CharTokenizer {
  /** Construct a new LetterTokenizer. */
  public LetterTokenizer(Reader in) {
    super(in);
  }

  /** Collects only characters which satisfy
   * {@link Character#isLetter(char)}.*/
  protected boolean isTokenChar(char c) {
    return Character.isLetter(c);
  }
}