bundles/org.simantics.document.server/src/org/simantics/document/server/client/AlphanumericComparator.java

   1 package org.simantics.document.server.client;
   2
   3 import java.util.Comparator;
   4
   5 /**
   6  * This is an updated version with enhancements made by Daniel Migowski,
   7  * Andre Bogus, and David Koelle
   8  *
   9  * To convert to use Templates (Java 1.5+):
  10  *   - Change "implements Comparator" to "implements Comparator<String>"
  11  *   - Change "compare(Object o1, Object o2)" to "compare(String s1, String s2)"
  12  *   - Remove the type checking and casting in compare().
  13  *
  14  * To use this class:
  15  *   Use the static "sort" method from the java.util.Collections class:
  16  *   Collections.sort(your list, new AlphanumComparator());
  17  */
  18 public class AlphanumericComparator implements Comparator<String>
  19 {
  20     private final boolean isDigit(char ch)
  21     {
  22         return ch >= 48 && ch <= 57;
  23     }
  24
  25     /** Length of string is passed in for improved efficiency (only need to calculate it once) **/
  26     private final String getChunk(String s, int slength, int marker)
  27     {
  28         StringBuilder chunk = new StringBuilder();
  29         char c = s.charAt(marker);
  30         chunk.append(c);
  31         marker++;
  32         if (isDigit(c))
  33         {
  34             while (marker < slength)
  35             {
  36                 c = s.charAt(marker);
  37                 if (!isDigit(c))
  38                     break;
  39                 chunk.append(c);
  40                 marker++;
  41             }
  42         } else
  43         {
  44             while (marker < slength)
  45             {
  46                 c = s.charAt(marker);
  47                 if (isDigit(c))
  48                     break;
  49                 chunk.append(c);
  50                 marker++;
  51             }
  52         }
  53         return chunk.toString();
  54     }
  55
  56     public int compare(String o1, String o2)
  57     {
  58         if (!(o1 instanceof String) || !(o2 instanceof String))
  59         {
  60             return 0;
  61         }
  62         String s1 = (String)o1;
  63         String s2 = (String)o2;
  64
  65         int thisMarker = 0;
  66         int thatMarker = 0;
  67         int s1Length = s1.length();
  68         int s2Length = s2.length();
  69
  70         while (thisMarker < s1Length && thatMarker < s2Length)
  71         {
  72             String thisChunk = getChunk(s1, s1Length, thisMarker);
  73             thisMarker += thisChunk.length();
  74
  75             String thatChunk = getChunk(s2, s2Length, thatMarker);
  76             thatMarker += thatChunk.length();
  77
  78             // If both chunks contain numeric characters, sort them numerically
  79             int result = 0;
  80             if (isDigit(thisChunk.charAt(0)) && isDigit(thatChunk.charAt(0)))
  81             {
  82                 // Simple chunk comparison by length.
  83                 int thisChunkLength = thisChunk.length();
  84                 result = thisChunkLength - thatChunk.length();
  85                 // If equal, the first different number counts
  86                 if (result == 0)
  87                 {
  88                     for (int i = 0; i < thisChunkLength; i++)
  89                     {
  90                         result = thisChunk.charAt(i) - thatChunk.charAt(i);
  91                         if (result != 0)
  92                         {
  93                             return result;
  94                         }
  95                     }
  96                 }
  97             } else
  98             {
  99                 result = thisChunk.compareTo(thatChunk);
 100             }
 101
 102             if (result != 0)
 103                 return result;
 104         }
 105
 106         return s1Length - s2Length;
 107     }
 108
 109 }
 110