    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.text.similarity;
    018
    019import java.util.Arrays;
    020
    021/**
    022 * A similarity algorithm indicating the percentage of matched characters between two character sequences.
    023 *
    024 * <p>
    025 * The Jaro measure is the weighted sum of percentage of matched characters
    026 * from each file and transposed characters. Winkler increased this measure
    027 * for matching initial characters.
    028 * </p>
    029 *
    030 * <p>
    031 * This implementation is based on the Jaro Winkler similarity algorithm
    032 * from <a href="http://en.wikipedia.org/wiki/Jaro%E2%80%93Winkler_distance">
    033 * http://en.wikipedia.org/wiki/Jaro%E2%80%93Winkler_distance</a>.
    034 * </p>
    035 *
    036 * <p>
    037 * This code has been adapted from Apache Commons Lang 3.3.
    038 * </p>
    039 *
    040 * @since 1.0
    041 */
    042public class JaroWinklerDistance implements SimilarityScore<Double> {
    043
    044    /**
    045     * Represents a failed index search.
    046     */
    047    public static final int INDEX_NOT_FOUND = -1;
    048
    049    /**
    050     * Find the Jaro Winkler Distance which indicates the similarity score
    051     * between two CharSequences.
    052     *
    053     * <pre>
    054     * distance.apply(null, null)          = IllegalArgumentException
    055     * distance.apply("","")               = 0.0
    056     * distance.apply("","a")              = 0.0
    057     * distance.apply("aaapppp", "")       = 0.0
    058     * distance.apply("frog", "fog")       = 0.93
    059     * distance.apply("fly", "ant")        = 0.0
    060     * distance.apply("elephant", "hippo") = 0.44
    061     * distance.apply("hippo", "elephant") = 0.44
    062     * distance.apply("hippo", "zzzzzzzz") = 0.0
    063     * distance.apply("hello", "hallo")    = 0.88
    064     * distance.apply("ABC Corporation", "ABC Corp") = 0.93
    065     * distance.apply("D N H Enterprises Inc", "D &amp; H Enterprises, Inc.") = 0.95
    066     * distance.apply("My Gym Children's Fitness Center", "My Gym. Childrens Fitness") = 0.92
    067     * distance.apply("PENNSYLVANIA", "PENNCISYLVNIA")    = 0.88
    068     * </pre>
    069     *
    070     * @param left the first CharSequence, must not be null
    071     * @param right the second CharSequence, must not be null
    072     * @return result distance
    073     * @throws IllegalArgumentException if either CharSequence input is {@code null}
    074     */
    075    @Override
    076    public Double apply(final CharSequence left, final CharSequence right) {
    077        final double defaultScalingFactor = 0.1;
    078
    079        if (left == null || right == null) {
    080            throw new IllegalArgumentException("CharSequences must not be null");
    081        }
    082
    083        final int[] mtp = matches(left, right);
    084        final double m = mtp[0];
    085        if (m == 0) {
    086            return 0D;
    087        }
    088        final double j = ((m / left.length() + m / right.length() + (m - (double) mtp[1] / 2) / m)) / 3;
    089        final double jw = j < 0.7D ? j : j + defaultScalingFactor * mtp[2] * (1D - j);
    090        return jw;
    091    }
    092
    093    /**
    094     * This method returns the Jaro-Winkler string matches, half transpositions, prefix array.
    095     *
    096     * @param first the first string to be matched
    097     * @param second the second string to be matched
    098     * @return mtp array containing: matches, half transpositions, and prefix
    099     */
    100    protected static int[] matches(final CharSequence first, final CharSequence second) {
    101        CharSequence max, min;
    102        if (first.length() > second.length()) {
    103            max = first;
    104            min = second;
    105        } else {
    106            max = second;
    107            min = first;
    108        }
    109        final int range = Math.max(max.length() / 2 - 1, 0);
    110        final int[] matchIndexes = new int[min.length()];
    111        Arrays.fill(matchIndexes, -1);
    112        final boolean[] matchFlags = new boolean[max.length()];
    113        int matches = 0;
    114        for (int mi = 0; mi < min.length(); mi++) {
    115            final char c1 = min.charAt(mi);
    116            for (int xi = Math.max(mi - range, 0), xn = Math.min(mi + range + 1, max.length()); xi < xn; xi++) {
    117                if (!matchFlags[xi] && c1 == max.charAt(xi)) {
    118                    matchIndexes[mi] = xi;
    119                    matchFlags[xi] = true;
    120                    matches++;
    121                    break;
    122                }
    123            }
    124        }
    125        final char[] ms1 = new char[matches];
    126        final char[] ms2 = new char[matches];
    127        for (int i = 0, si = 0; i < min.length(); i++) {
    128            if (matchIndexes[i] != -1) {
    129                ms1[si] = min.charAt(i);
    130                si++;
    131            }
    132        }
    133        for (int i = 0, si = 0; i < max.length(); i++) {
    134            if (matchFlags[i]) {
    135                ms2[si] = max.charAt(i);
    136                si++;
    137            }
    138        }
    139        int halfTranspositions = 0;
    140        for (int mi = 0; mi < ms1.length; mi++) {
    141            if (ms1[mi] != ms2[mi]) {
    142                halfTranspositions++;
    143            }
    144        }
    145        int prefix = 0;
    146        for (int mi = 0; mi < Math.min(4, min.length()); mi++) {
    147            if (first.charAt(mi) == second.charAt(mi)) {
    148                prefix++;
    149            } else {
    150                break;
    151            }
    152        }
    153        return new int[] {matches, halfTranspositions, prefix};
    154    }
    155
    156}