Eric Kok
12 years ago
4 changed files with 121 additions and 9 deletions
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package org.transdroid.daemon; |
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/* |
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* The Alphanum Algorithm is an improved sorting algorithm for strings |
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* containing numbers. Instead of sorting numbers in ASCII order like |
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* a standard sort, this algorithm sorts numbers in numeric order. |
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* |
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* The Alphanum Algorithm is discussed at http://www.DaveKoelle.com
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* |
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* This is an updated version with enhancements made by Daniel Migowski, |
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* Andre Bogus, and David Koelle |
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* |
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* This library is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or any later version. |
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* |
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* This library is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with this library; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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*/ |
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import java.util.Comparator; |
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public class AlphanumComparator implements Comparator<String> { |
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private final boolean isDigit(char ch) { |
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return ch >= 48 && ch <= 57; |
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} |
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/** Length of string is passed in for improved efficiency (only need to calculate it once) **/ |
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private final String getChunk(String s, int slength, int marker) { |
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StringBuilder chunk = new StringBuilder(); |
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char c = s.charAt(marker); |
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chunk.append(c); |
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marker++; |
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if (isDigit(c)) { |
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while (marker < slength) { |
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c = s.charAt(marker); |
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if (!isDigit(c)) |
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break; |
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chunk.append(c); |
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marker++; |
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} |
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} else { |
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while (marker < slength) { |
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c = s.charAt(marker); |
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if (isDigit(c)) |
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break; |
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chunk.append(c); |
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marker++; |
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} |
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} |
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return chunk.toString(); |
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} |
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public int compare(String o1, String o2) { |
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if (!(o1 instanceof String) || !(o2 instanceof String)) { |
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return 0; |
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} |
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String s1 = (String) o1; |
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String s2 = (String) o2; |
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int thisMarker = 0; |
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int thatMarker = 0; |
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int s1Length = s1.length(); |
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int s2Length = s2.length(); |
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while (thisMarker < s1Length && thatMarker < s2Length) { |
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String thisChunk = getChunk(s1, s1Length, thisMarker); |
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thisMarker += thisChunk.length(); |
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String thatChunk = getChunk(s2, s2Length, thatMarker); |
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thatMarker += thatChunk.length(); |
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// If both chunks contain numeric characters, sort them numerically
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int result = 0; |
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if (isDigit(thisChunk.charAt(0)) && isDigit(thatChunk.charAt(0))) { |
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// Simple chunk comparison by length.
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int thisChunkLength = thisChunk.length(); |
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result = thisChunkLength - thatChunk.length(); |
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// If equal, the first different number counts
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if (result == 0) { |
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for (int i = 0; i < thisChunkLength; i++) { |
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result = thisChunk.charAt(i) - thatChunk.charAt(i); |
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if (result != 0) { |
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return result; |
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} |
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} |
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} |
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} else { |
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result = thisChunk.compareTo(thatChunk); |
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} |
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if (result != 0) |
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return result; |
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} |
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return s1Length - s2Length; |
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} |
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} |
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