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/*
* 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.
*/
package org.apache.openjpa.lib.util;
import java.util.Arrays;
import java.util.Collection;
/**
* Utilities for calculating string distance.
*
* @author Marc Prud'hommeaux
*/
public class StringDistance {
/**
* Returns the candidate string with the closest Levenshtein distance
* to the given string.
*
* @see #getClosestLevenshteinDistance(String,Collection,int)
*/
public static String getClosestLevenshteinDistance(String str,
String[] candidates) {
if (candidates == null)
return null;
return getClosestLevenshteinDistance(str, Arrays.asList(candidates));
}
/**
* Returns the candidate string with the closest Levenshtein distance
* to the given string.
*
* @see #getClosestLevenshteinDistance(String,Collection,int)
*/
public static String getClosestLevenshteinDistance(String str,
Collection candidates) {
return getClosestLevenshteinDistance(str, candidates,
Integer.MAX_VALUE);
}
/**
* Returns the candidate string with the closest Levenshtein distance
* to the given string.
*
* @see #getClosestLevenshteinDistance(String,Collection,int)
*/
public static String getClosestLevenshteinDistance(String str,
String[] candidates, int threshold) {
if (candidates == null)
return null;
return getClosestLevenshteinDistance(str, Arrays.asList(candidates),
threshold);
}
/**
* Returns the candidate string with the closest Levenshtein distance
* to the given string and using the threshold as the specified
* percentage of the length of the candidate string(0.0f-1.0f).
*
* @see #getClosestLevenshteinDistance(String,Collection,int)
*/
public static String getClosestLevenshteinDistance(String str,
String[] candidates, float thresholdPercentage) {
if (candidates == null)
return null;
return getClosestLevenshteinDistance(str, Arrays.asList(candidates),
thresholdPercentage);
}
/**
* Returns the candidate string with the closest Levenshtein distance
* to the given string and using the threshold as the specified
* percentage of the length of the candidate string(0.0f-1.0f).
*
* @see #getClosestLevenshteinDistance(String,Collection,int)
*/
public static String getClosestLevenshteinDistance(String str,
Collection candidates, float thresholdPercentage) {
if (str == null)
return null;
thresholdPercentage = Math.min(thresholdPercentage, 1.0f);
thresholdPercentage = Math.max(thresholdPercentage, 0.0f);
return getClosestLevenshteinDistance(str, candidates,
(int) (str.length() * thresholdPercentage));
}
/**
* Returns the candidate string with the closest Levenshtein distance
* to the given string.
*
* @param str the string to check
* @param candidates the list of strings to test against
* @param threshold the threshold distance a candidate must meet
* @see #getLevenshteinDistance
*/
public static String getClosestLevenshteinDistance(String str,
Collection candidates, int threshold) {
if (candidates == null || candidates.isEmpty())
return null;
String minString = null;
int minValue = Integer.MAX_VALUE;
for(String candidate : candidates) {
int distance = getLevenshteinDistance(str, candidate);
if (distance < minValue) {
minValue = distance;
minString = candidate;
}
}
// return the lowest close string only if we surpass the threshhold
if (minValue <= threshold)
return minString;
else
return null;
}
/**
* Returns the Levenshtein distance between the two strings.
* The distance is the minimum number of changes that need to be
* applied to the first string in order to get to the second
* string. For details of the algorithm, see
*
* http://en.wikipedia.org/wiki/Levenshtein_distance.
*/
public static int getLevenshteinDistance(String s, String t) {
int n = s.length();
int m = t.length();
if (n == 0)
return m;
if (m == 0)
return n;
int[][] matrix = new int[n + 1][m + 1];
for (int i = 0; i <= n; i++)
matrix[i][0] = i;
for (int j = 0; j <= m; j++)
matrix[0][j] = j;
for (int i = 1; i <= n; i++) {
int si = s.charAt(i - 1);
for (int j = 1; j <= m; j++) {
int tj = t.charAt(j - 1);
int cost;
if (si == tj)
cost = 0;
else
cost = 1;
matrix[i][j] = min(matrix[i - 1][j] + 1, matrix[i][j - 1] + 1,
matrix[i - 1][j - 1] + cost);
}
}
return matrix[n][m];
}
private static int min(int a, int b, int c) {
int mi = a;
if (b < mi)
mi = b;
if (c < mi)
mi = c;
return mi;
}
}
