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 - mtp[1]) / m)) / 3;
089        final double jw = j < 0.7D ? j : j + Math.min(defaultScalingFactor, 1D / mtp[3]) * mtp[2] * (1D - j);
090        return jw;
091    }
092
093    /**
094     * This method returns the Jaro-Winkler string matches, transpositions, prefix, max 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, transpositions, prefix, and max length
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 transpositions = 0;
140        for (int mi = 0; mi < ms1.length; mi++) {
141            if (ms1[mi] != ms2[mi]) {
142                transpositions++;
143            }
144        }
145        int prefix = 0;
146        for (int mi = 0; mi < min.length(); mi++) {
147            if (first.charAt(mi) == second.charAt(mi)) {
148                prefix++;
149            } else {
150                break;
151            }
152        }
153        return new int[] {matches, transpositions / 2, prefix, max.length()};
154    }
155
156}