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Old JAXB Core module. Contains sources required by XJC, JXC and Runtime modules with dependencies.
There is a newer version: 4.0.5
/*
 * Copyright (c) 1997, 2020 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 org.glassfish.jaxb.core.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