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 }