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
021import org.apache.commons.lang3.StringUtils;
022
023/**
024 * A similarity algorithm indicating the percentage of matched characters between two character sequences.
025 *
026 * <p>
027 * The Jaro measure is the weighted sum of percentage of matched characters
028 * from each file and transposed characters. Winkler increased this measure
029 * for matching initial characters.
030 * </p>
031 *
032 * <p>
033 * This implementation is based on the Jaro Winkler similarity algorithm
034 * from <a href="http://en.wikipedia.org/wiki/Jaro%E2%80%93Winkler_distance">
035 * http://en.wikipedia.org/wiki/Jaro%E2%80%93Winkler_distance</a>.
036 * </p>
037 *
038 * <p>
039 * This code has been adapted from Apache Commons Lang 3.3.
040 * </p>
041 *
042 * @since 1.7
043 */
044public class JaroWinklerSimilarity implements SimilarityScore<Double> {
045
046    /**
047     * Computes the Jaro Winkler Similarity between two character sequences.
048     *
049     * <pre>
050     * sim.apply(null, null)          = IllegalArgumentException
051     * sim.apply("foo", null)         = IllegalArgumentException
052     * sim.apply(null, "foo")         = IllegalArgumentException
053     * sim.apply("", "")              = 1.0
054     * sim.apply("foo", "foo")        = 1.0
055     * sim.apply("foo", "foo ")       = 0.94
056     * sim.apply("foo", "foo  ")      = 0.91
057     * sim.apply("foo", " foo ")      = 0.87
058     * sim.apply("foo", "  foo")      = 0.51
059     * sim.apply("", "a")             = 0.0
060     * sim.apply("aaapppp", "")       = 0.0
061     * sim.apply("frog", "fog")       = 0.93
062     * sim.apply("fly", "ant")        = 0.0
063     * sim.apply("elephant", "hippo") = 0.44
064     * sim.apply("hippo", "elephant") = 0.44
065     * sim.apply("hippo", "zzzzzzzz") = 0.0
066     * sim.apply("hello", "hallo")    = 0.88
067     * sim.apply("ABC Corporation", "ABC Corp") = 0.91
068     * sim.apply("D N H Enterprises Inc", "D &amp; H Enterprises, Inc.") = 0.95
069     * sim.apply("My Gym Children's Fitness Center", "My Gym. Childrens Fitness") = 0.92
070     * sim.apply("PENNSYLVANIA", "PENNCISYLVNIA") = 0.88
071     * </pre>
072     *
073     * @param left the first CharSequence, must not be null
074     * @param right the second CharSequence, must not be null
075     * @return result similarity
076     * @throws IllegalArgumentException if either CharSequence input is {@code null}
077     */
078    @Override
079    public Double apply(final CharSequence left, final CharSequence right) {
080        final double defaultScalingFactor = 0.1;
081
082        if (left == null || right == null) {
083            throw new IllegalArgumentException("CharSequences must not be null");
084        }
085
086        if (StringUtils.equals(left, right)) {
087            return 1d;
088        }
089
090        final int[] mtp = matches(left, right);
091        final double m = mtp[0];
092        if (m == 0) {
093            return 0d;
094        }
095        final double j = ((m / left.length() + m / right.length() + (m - (double) mtp[1] / 2) / m)) / 3;
096        final double jw = j < 0.7d ? j : j + defaultScalingFactor * mtp[2] * (1d - j);
097        return jw;
098    }
099
100    /**
101     * This method returns the Jaro-Winkler string matches, half transpositions, prefix array.
102     *
103     * @param first the first string to be matched
104     * @param second the second string to be matched
105     * @return mtp array containing: matches, half transpositions, and prefix
106     */
107    protected static int[] matches(final CharSequence first, final CharSequence second) {
108        CharSequence max, min;
109        if (first.length() > second.length()) {
110            max = first;
111            min = second;
112        } else {
113            max = second;
114            min = first;
115        }
116        final int range = Math.max(max.length() / 2 - 1, 0);
117        final int[] matchIndexes = new int[min.length()];
118        Arrays.fill(matchIndexes, -1);
119        final boolean[] matchFlags = new boolean[max.length()];
120        int matches = 0;
121        for (int mi = 0; mi < min.length(); mi++) {
122            final char c1 = min.charAt(mi);
123            for (int xi = Math.max(mi - range, 0), xn = Math.min(mi + range + 1, max.length()); xi < xn; xi++) {
124                if (!matchFlags[xi] && c1 == max.charAt(xi)) {
125                    matchIndexes[mi] = xi;
126                    matchFlags[xi] = true;
127                    matches++;
128                    break;
129                }
130            }
131        }
132        final char[] ms1 = new char[matches];
133        final char[] ms2 = new char[matches];
134        for (int i = 0, si = 0; i < min.length(); i++) {
135            if (matchIndexes[i] != -1) {
136                ms1[si] = min.charAt(i);
137                si++;
138            }
139        }
140        for (int i = 0, si = 0; i < max.length(); i++) {
141            if (matchFlags[i]) {
142                ms2[si] = max.charAt(i);
143                si++;
144            }
145        }
146        int halfTranspositions = 0;
147        for (int mi = 0; mi < ms1.length; mi++) {
148            if (ms1[mi] != ms2[mi]) {
149                halfTranspositions++;
150            }
151        }
152        int prefix = 0;
153        for (int mi = 0; mi < Math.min(4, min.length()); mi++) {
154            if (first.charAt(mi) == second.charAt(mi)) {
155                prefix++;
156            } else {
157                break;
158            }
159        }
160        return new int[] {matches, halfTranspositions, prefix};
161    }
162
163}