content: package org.apache.lucene.search.spell;
  
  /**
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  import java.util.Arrays;
  
  public class JaroWinklerDistance implements StringDistance {
  
    private float threshold = 0.7f;
  
    private int[] matches(String s1, String s2) {
      String max, min;
      if (s1.length() > s2.length()) {
        max = s1;
        min = s2;
      } else {
        max = s2;
        min = s1;
      }
      int range = Math.max(max.length() / 2 - 1, 0);
      int[] matchIndexes = new int[min.length()];
      Arrays.fill(matchIndexes, -1);
      boolean[] matchFlags = new boolean[max.length()];
      int matches = 0;
      for (int mi = 0; mi < min.length(); mi++) {
        char c1 = min.charAt(mi);
        for (int xi = Math.max(mi - range, 0), xn = Math.min(mi + range + 1, max
            .length()); xi < xn; xi++) {
          if (!matchFlags[xi] && c1 == max.charAt(xi)) {
            matchIndexes[mi] = xi;
            matchFlags[xi] = true;
            matches++;
            break;
          }
        }
      }
      char[] ms1 = new char[matches];
      char[] ms2 = new char[matches];
      for (int i = 0, si = 0; i < min.length(); i++) {
        if (matchIndexes[i] != -1) {
          ms1[si] = min.charAt(i);
          si++;
        }
      }
      for (int i = 0, si = 0; i < max.length(); i++) {
        if (matchFlags[i]) {
          ms2[si] = max.charAt(i);
          si++;
        }
      }
      int transpositions = 0;
      for (int mi = 0; mi < ms1.length; mi++) {
        if (ms1[mi] != ms2[mi]) {
          transpositions++;
        }
      }
      int prefix = 0;
      for (int mi = 0; mi < min.length(); mi++) {
        if (s1.charAt(mi) == s2.charAt(mi)) {
          prefix++;
        } else {
          break;
        }
      }
      return new int[] { matches, transpositions / 2, prefix, max.length() };
    }
  
    public float getDistance(String s1, String s2) {
      int[] mtp = matches(s1, s2);
      float m = mtp[0];
      if (m == 0) {
        return 0f;
      }
      float j = ((m / s1.length() + m / s2.length() + (m - mtp[1]) / m)) / 3;
      float jw = j < getThreshold() ? j : j + Math.min(0.1f, 1f / mtp[3]) * mtp[2]
          * (1 - j);
      return jw;
    }
  
    /**
     * Sets the threshold used to determine when Winkler bonus should be used.
     * Set to a negative value to get the Jaro distance.
     * @param threshold the new value of the threshold
     */
    public void setThreshold(float threshold) {
      this.threshold = threshold;
    }
  
    /**
     * Returns the current value of the threshold used for adding the Winkler bonus.
     * The default value is 0.7.
     * @return the current value of the threshold
     */
    public float getThreshold() {
      return threshold;
    }
  }
  