AlphaNumericComparator.java

//The MIT License
//
// Copyright (c) 2003 Ron Alford, Mike Grove, Bijan Parsia, Evren Sirin
//
// 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:
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// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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package org.apache.solr.hadoop;

import java.util.Comparator;

/**
 * This is a comparator to perform a mix of alphabetical+numeric comparison. For
 * example, if there is a list {"test10", "test2", "test150", "test25", "test1"}
 * then what we generally expect from the ordering is the result {"test1",
 * "test2", "test10", "test25", "test150"}. However, standard lexigraphic
 * ordering does not do that and "test10" comes before "test2". This class is
 * provided to overcome that problem. This functionality is useful to sort the
 * benchmark files (like the ones in in DL-benchmark-suite) from smallest to the
 * largest. Comparisons are done on the String values retuned by toString() so
 * care should be taken when this comparator is used to sort arbitrary Java
 * objects.
 * 
 */
final class AlphaNumericComparator implements Comparator {

    public AlphaNumericComparator() {
    }

    public int compare(Object o1, Object o2) {
        String s1 = o1.toString();
        String s2 = o2.toString();
        int n1 = s1.length(), n2 = s2.length();
        int i1 = 0, i2 = 0;
        while (i1 < n1 && i2 < n2) {
            int p1 = i1;
            int p2 = i2;
            char c1 = s1.charAt(i1++);
            char c2 = s2.charAt(i2++);
            if(c1 != c2) {
                if (Character.isDigit(c1) && Character.isDigit(c2)) {
                    int value1 = 0, value2 = 0;
                    while (i1 < n1 && Character.isDigit(c1 = s1.charAt(i1))) {
                      i1++;
                    }
                    value1 = Integer.parseInt(s1.substring(p1, i1));
                    while (i2 < n2 && Character.isDigit(c2 = s2.charAt(i2))) {
                      i2++;
                    }
                    value2 = Integer.parseInt(s2.substring(p2, i2));                    
                    if (value1 != value2) {
                      return value1 - value2;
                    }
                }
                return c1 - c2;
            }
        }

        return n1 - n2;
    }
}