1 | package org.openstreetmap.josm.tools;
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2 |
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3 | /*
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4 | * The Alphanum Algorithm is an improved sorting algorithm for strings
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5 | * containing numbers. Instead of sorting numbers in ASCII order like a standard
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6 | * sort, this algorithm sorts numbers in numeric order.
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7 | *
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8 | * The Alphanum Algorithm is discussed at http://www.DaveKoelle.com
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9 | *
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10 | *
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11 | * This library is free software; you can redistribute it and/or modify it under
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12 | * the terms of the GNU Lesser General Public License as published by the Free
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13 | * Software Foundation; either version 2.1 of the License, or any later version.
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14 | *
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15 | * This library is distributed in the hope that it will be useful, but WITHOUT
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16 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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17 | * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
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18 | * details.
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19 | *
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20 | * You should have received a copy of the GNU Lesser General Public License
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21 | * along with this library; if not, write to the Free Software Foundation, Inc.,
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22 | * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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23 | *
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24 | */
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25 | import java.util.Comparator;
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26 |
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27 | /**
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28 | * The Alphanum Algorithm is an improved sorting algorithm for strings
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29 | * containing numbers: Instead of sorting numbers in ASCII order like a standard
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30 | * sort, this algorithm sorts numbers in numeric order.
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31 | *
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32 | * The Alphanum Algorithm is discussed at http://www.DaveKoelle.com
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33 | *
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34 | * This is an updated version with enhancements made by Daniel Migowski, Andre
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35 | * Bogus, and David Koelle.
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36 | *
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37 | */
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38 | public class AlphanumComparator implements Comparator<String> {
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39 |
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40 | /**
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41 | * Length of string is passed in for improved efficiency (only need to
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42 | * calculate it once) *
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43 | */
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44 | private String getChunk(String s, int slength, int marker) {
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45 | StringBuilder chunk = new StringBuilder();
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46 | char c = s.charAt(marker);
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47 | chunk.append(c);
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48 | marker++;
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49 | if (Character.isDigit(c)) {
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50 | while (marker < slength) {
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51 | c = s.charAt(marker);
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52 | if (!Character.isDigit(c)) {
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53 | break;
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54 | }
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55 | chunk.append(c);
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56 | marker++;
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57 | }
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58 | } else {
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59 | while (marker < slength) {
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60 | c = s.charAt(marker);
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61 | if (Character.isDigit(c)) {
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62 | break;
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63 | }
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64 | chunk.append(c);
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65 | marker++;
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66 | }
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67 | }
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68 | return chunk.toString();
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69 | }
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70 |
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71 | @Override
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72 | public int compare(String s1, String s2) {
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73 | if (s1 == null && s2 == null) {
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74 | return 0;
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75 | } else if (s1 == null) {
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76 | return -1;
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77 | } else if (s2 == null) {
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78 | return 1;
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79 | }
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80 |
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81 | int thisMarker = 0;
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82 | int thatMarker = 0;
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83 | int s1Length = s1.length();
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84 | int s2Length = s2.length();
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85 |
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86 | while (thisMarker < s1Length && thatMarker < s2Length) {
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87 | String thisChunk = getChunk(s1, s1Length, thisMarker);
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88 | thisMarker += thisChunk.length();
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89 |
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90 | String thatChunk = getChunk(s2, s2Length, thatMarker);
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91 | thatMarker += thatChunk.length();
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92 |
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93 | // If both chunks contain numeric characters, sort them numerically
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94 | int result;
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95 | if (Character.isDigit(thisChunk.charAt(0)) && Character.isDigit(thatChunk.charAt(0))) {
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96 | // Simple chunk comparison by length.
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97 | int thisChunkLength = thisChunk.length();
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98 | result = thisChunkLength - thatChunk.length();
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99 | // If equal, the first different number counts
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100 | if (result == 0) {
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101 | for (int i = 0; i < thisChunkLength; i++) {
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102 | result = thisChunk.charAt(i) - thatChunk.charAt(i);
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103 | if (result != 0) {
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104 | return result;
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105 | }
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106 | }
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107 | }
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108 | } else {
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109 | result = thisChunk.compareTo(thatChunk);
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110 | }
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111 |
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112 | if (result != 0) {
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113 | return result;
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114 | }
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115 | }
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116 |
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117 | return s1Length - s2Length;
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118 | }
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119 | }
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