1 /*
   2  * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  *
   8  *   - Redistributions of source code must retain the above copyright
   9  *     notice, this list of conditions and the following disclaimer.
  10  *
  11  *   - Redistributions in binary form must reproduce the above copyright
  12  *     notice, this list of conditions and the following disclaimer in the
  13  *     documentation and/or other materials provided with the distribution.
  14  *
  15  *   - Neither the name of Oracle nor the names of its
  16  *     contributors may be used to endorse or promote products derived
  17  *     from this software without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
  20  * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  21  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  23  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  24  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  25  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  26  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  27  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  28  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  29  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  30  */
  31 
  32 /*
  33  * This source code is provided to illustrate the usage of a given feature
  34  * or technique and has been deliberately simplified. Additional steps
  35  * required for a production-quality application, such as security checks,
  36  * input validation and proper error handling, might not be present in
  37  * this sample code.
  38  */
  39 
  40 package comparator;
  41 
  42 import java.io.Serializable;
  43 import java.util.Comparator;
  44 
  45 public class AlphaNumericComparator
  46         implements Comparator<CharSequence>, Serializable
  47 {
  48     private static final long serialVersionUID = 0x77164074580FAC97L;
  49 
  50     /**
  51      * Counts how many consequtive characters in the string {@code o}
  52      * are digits, starting from the position {@code from}.
  53      */
  54     private int countDigits(CharSequence o, int from) {
  55         final int oLength = o.length();
  56         for (int i = from; ; ++i) {
  57             if (i == oLength || !Character.isDigit(o.charAt(i))) {
  58                 return (i - from);
  59             }
  60         }
  61     }
  62 
  63     @Override
  64     public int compare(CharSequence o1, CharSequence o2) {
  65         final int minLength = Integer.min(o1.length(), o2.length());
  66         int numStart1 = 0;
  67         int index = 0;
  68 
  69         // skip common prefix of the arguments
  70         while (index < minLength &&
  71                 Character.compare(o1.charAt(index),
  72                         o2.charAt(index)) == 0)
  73         {
  74             if (!Character.isDigit(o1.charAt(index++))) {
  75                 numStart1 = index;
  76             }
  77         }
  78 
  79         int numCount1 = index - numStart1;
  80         if (numCount1 > 0 ||
  81                 (index < minLength &&
  82                         Character.isDigit(o1.charAt(index)) &&
  83                         Character.isDigit(o2.charAt(index))))
  84         {
  85             // first different character is a digit
  86             int numCount2 = numCount1;
  87             int numStart2 = numStart1;
  88 
  89             numCount1 += countDigits(o1, index);
  90             numCount2 += countDigits(o2, index);
  91 
  92             int numCountWithZeros1 = numCount1;
  93             int numCountWithZeros2 = numCount2;
  94 
  95             while (numCount1 < numCount2) {
  96                 if (Character.digit(o2.charAt(numStart2), 10) != 0) {
  97                     // leading digit of numeric part of o2 isn't zero
  98                     return -1;
  99                 }
 100                 numStart2++;
 101                 numCount2--;
 102             }
 103 
 104             while (numCount2 < numCount1) {
 105                 if (Character.digit(o1.charAt(numStart1), 10) != 0) {
 106                     // leading digit of numeric part of o1 isn't zero
 107                     return 1;
 108                 }
 109                 numStart1++;
 110                 numCount1--;
 111             }
 112 
 113             // here numCount1 == numCount2;
 114             while (numCount1-- > 0) {
 115                 int res = Character.compare(o1.charAt(numStart1++),
 116                         o2.charAt(numStart2++));
 117                 if (res != 0) {
 118                     return res;
 119                 }
 120             }
 121 
 122             if (numCountWithZeros1 != numCountWithZeros2) {
 123                 return (numCountWithZeros1 < numCountWithZeros2) ? -1 : 1;
 124             }
 125 
 126         }
 127 
 128         // otherwise, compare literally
 129         for (;; ++index) {
 130             if (index < o1.length()) {
 131                 if (index < o2.length()) {
 132                     int res = Character.compare(o1.charAt(index),
 133                             o2.charAt(index));
 134                     if (res != 0) {
 135                         return res;
 136                     }
 137                 } else {
 138                     return 1;
 139                 }
 140             } else {
 141                 if (index < o2.length()) {
 142                     return -1;
 143                 }
 144                 return 0;
 145             }
 146         }
 147     }
 148 }