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/*
 * Copyright (c) 1997, 2018 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0, which is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

package com.sun.xml.bind.v2.util;

import java.util.AbstractMap;
import java.util.Arrays;
import java.util.Collection;
import java.util.WeakHashMap;

/**
 * Computes the string edit distance.
 * 
 * 

* Refer to a computer science text book for the definition * of the "string edit distance". * * @author * Kohsuke Kawaguchi ([email protected]) */ public class EditDistance { /** * Weak results cache to avoid additional computations. * Because of high complexity caching is required. */ private static final WeakHashMap, Integer> CACHE = new WeakHashMap, Integer>(); /** * Computes the edit distance between two strings. * *

* The complexity is O(nm) where n=a.length() and m=b.length(). */ public static int editDistance( String a, String b ) { // let's check cache AbstractMap.SimpleEntry entry = new AbstractMap.SimpleEntry(a, b); // using this class to avoid creation of my own which will handle PAIR of values Integer result = null; if (CACHE.containsKey(entry)) result = CACHE.get(entry); // looks like we have it if (result == null) { result = new EditDistance(a, b).calc(); CACHE.put(entry, result); // cache the result } return result; } /** * Finds the string in the group closest to * key and returns it. * * @return null if group.length==0. */ public static String findNearest( String key, String[] group ) { return findNearest(key, Arrays.asList(group)); } /** * Finds the string in the group closest to * key and returns it. * * @return null if group.length==0. */ public static String findNearest( String key, Collection group ) { int c = Integer.MAX_VALUE; String r = null; for (String s : group) { int ed = editDistance(key,s); if( c>ed ) { c = ed; r = s; } } return r; } /** cost vector. */ private int[] cost; /** back buffer. */ private int[] back; /** Two strings to be compared. */ private final String a,b; private EditDistance( String a, String b ) { this.a=a; this.b=b; cost = new int[a.length()+1]; back = new int[a.length()+1]; // back buffer for( int i=0; i<=a.length(); i++ ) cost[i] = i; } /** * Swaps two buffers. */ private void flip() { int[] t = cost; cost = back; back = t; } private int min(int a,int b,int c) { return Math.min(a,Math.min(b,c)); } private int calc() { for( int j=0; j





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