libjava/classpath/tools/gnu/classpath/tools/giop/grmic/HashFinder.java

   1 /* HashFinder.java -- finds the hash character.
   2    Copyright (C) 2006 Free Software Foundation
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301 USA.
  20 */
  21
  22
  23 package gnu.classpath.tools.giop.grmic;
  24
  25 import java.util.HashSet;
  26
  27 /**
  28  * This class finds the hash character (the most different character in
  29  * the passed array of strings). This character is used to accelerate the
  30  * method invocation by name.
  31  *
  32  * @author Audrius Meskauskas (AudriusA@Bioinformatics.org)
  33  */
  34 public class HashFinder
  35 {
  36    /**
  37    * Find the hash char position in the given collection of strings.
  38    *
  39    * @param strings the string collection
  40    *
  41    * @return the optimal hash character position, always less then the
  42    * length of the shortest string.
  43    */
  44   public int findHashCharPosition(String[] strings)
  45   {
  46     // Find the length of the shortest string:
  47
  48     int l = strings[0].length();
  49     for (int i = 1; i < strings.length; i++)
  50       {
  51         if (strings[i].length() < l)
  52           l = strings[i].length();
  53       }
  54
  55     // Find the position with the smallest number of the matching characters:
  56     HashSet[] charLists = new HashSet[l];
  57
  58     for (int i = 0; i < charLists.length; i++)
  59       {
  60         charLists[i] = new HashSet(strings.length);
  61       }
  62
  63     for (int i = 0; i < strings.length; i++)
  64       for (int p = 0; p < l; p++)
  65         {
  66           charLists[p].add(new Integer(strings[i].charAt(p)));
  67         }
  68
  69     int m = 0;
  70     int v = charLists[0].size();
  71
  72     for (int i = 1; i < charLists.length; i++)
  73       {
  74         // Replace on equality also, seeking the hash char closer to the end
  75         // of line.
  76         if (charLists[i].size()>=v)
  77           {
  78             m = i;
  79             v = charLists[i].size();
  80           }
  81       }
  82     return m;
  83   }
  84 }