The Alphanum Algorithm is an improved sorting algorithm for strings containing numbers. Instead of sorting numbers in ASCII order like a standard sort, this algorithm sorts numbers in numeric order.
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;
/**
* @ClassName: AlphanumComparator
* @Description: The Alphanum Algorithm is an improved sorting algorithm for strings
* containing numbers. Instead of sorting numbers in ASCII order like
* a standard sort, this algorithm sorts numbers in numeric order.
*
* The Alphanum Algorithm is discussed at http://www.DaveKoelle.com
*
* Released under the MIT License - https://opensource.org/licenses/MIT
*
* Copyright 2007-2017 David Koelle
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
* OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
* USE OR OTHER DEALINGS IN THE SOFTWARE.
*
* This is an updated version with enhancements made by Daniel Migowski,
* Andre Bogus, and David Koelle. Updated by David Koelle in 2017.
* <p>
* To use this class:
* Use the static "sort" method from the java.util.Collections class:
* Collections.sort(your list, new AlphanumComparator());
*
* @Author: Aman
* @Date: 2019-08-20 16:56
* @Version: 1.0
*/
public class AlphanumComparator implements Comparator<String> {
private final boolean isDigit(char ch) {
return ((ch >= 48) && (ch <= 57));
}
/**
* Length of string is passed in for improved efficiency (only need to calculate it once)
**/
private final String getChunk(String s, int slength, int marker) {
StringBuilder chunk = new StringBuilder();
char c = s.charAt(marker);
chunk.append(c);
marker++;
if (isDigit(c)) {
while (marker < slength) {
c = s.charAt(marker);
if (!isDigit(c)) {
break;
}
chunk.append(c);
marker++;
}
} else {
while (marker < slength) {
c = s.charAt(marker);
if (isDigit(c)) {
break;
}
chunk.append(c);
marker++;
}
}
return chunk.toString();
}
@Override
public int compare(String s1, String s2) {
if ((s1 == null) || (s2 == null)) {
return 0;
}
int thisMarker = 0;
int thatMarker = 0;
int s1Length = s1.length();
int s2Length = s2.length();
while (thisMarker < s1Length && thatMarker < s2Length) {
String thisChunk = getChunk(s1, s1Length, thisMarker);
thisMarker += thisChunk.length();
String thatChunk = getChunk(s2, s2Length, thatMarker);
thatMarker += thatChunk.length();
// If both chunks contain numeric characters, sort them numerically
int result = 0;
if (isDigit(thisChunk.charAt(0)) && isDigit(thatChunk.charAt(0))) {
// Simple chunk comparison by length.
int thisChunkLength = thisChunk.length();
result = thisChunkLength - thatChunk.length();
// If equal, the first different number counts
if (result == 0) {
for (int i = 0; i < thisChunkLength; i++) {
result = thisChunk.charAt(i) - thatChunk.charAt(i);
if (result != 0) {
return result;
}
}
}
} else {
result = thisChunk.compareTo(thatChunk);
}
if (result != 0) {
return result;
}
}
return s1Length - s2Length;
}
/**
* Shows an example of how the comparator works.
* Feel free to delete this in your own code!
*/
public static void main(String[] args) {
List<String> values = Arrays.asList("dazzle2", "dazzle10", "dazzle1", "dazzle2.7", "dazzle2.10", "2", "10", "1", "EctoMorph6", "EctoMorph62", "EctoMorph7");
System.out.println(values.stream().sorted(new AlphanumComparator()).collect(Collectors.joining(" ")));
}
}