001/*
002 *  Units of Measurement Common Library for Java
003 *  Copyright (c) 2005-2016, Jean-Marie Dautelle, Werner Keil, V2COM.
004 *
005 * All rights reserved.
006 *
007 * Redistribution and use in source and binary forms, with or without modification,
008 * are permitted provided that the following conditions are met:
009 *
010 * 1. Redistributions of source code must retain the above copyright notice,
011 *    this list of conditions and the following disclaimer.
012 *
013 * 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions
014 *    and the following disclaimer in the documentation and/or other materials provided with the distribution.
015 *
016 * 3. Neither the name of JSR-363, Unit-API nor the names of its contributors may be used to endorse or promote products
017 *    derived from this software without specific prior written permission.
018 *
019 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
020 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
021 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
022 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
023 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
024 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
025 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
026 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
027 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
028 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029 */
030package tec.uom.lib.common.util;
031
032import static java.lang.Character.isDigit;
033import static java.lang.Character.isSpaceChar;
034
035import java.util.Comparator;
036
037/**
038 * Compares two {@linkplain Number} objects with each other
039 * @author Werner
040 * @version 0.1
041 * @since 1.0.2
042 */
043public class NumberComparator implements Comparator<Number> {
044
045        private NumberComparator() {
046                // Singleton
047        }
048
049        protected static char charAt(String s, int i) {
050                if (i >= s.length()) {
051                        return '\000';
052                }
053
054                return s.charAt(i);
055        }
056
057        protected int compareRight(String a, String b) {
058                int bias = 0;
059                int ia = 0;
060                int ib = 0;
061                while (true) {
062                        char ca = charAt(a, ia);
063                        char cb = charAt(b, ib);
064
065                        if ((!isDigit(ca)) && (!isDigit(cb))) {
066                                return bias;
067                        }
068                        if (!isDigit(ca)) {
069                                return -1;
070                        }
071                        if (!isDigit(cb)) {
072                                return 1;
073                        }
074                        if (ca < cb) {
075                                if (bias == 0) {
076                                        bias = -1;
077                                }
078                        } else if (ca > cb) {
079                                if (bias == 0)
080                                        bias = 1;
081                        } else if ((ca == 0) && (cb == 0))
082                                return bias;
083                        ia++;
084                        ib++;
085                }
086        }
087
088        public int compare(Number o1, Number o2) {
089                String a = o1.toString();
090                String b = o2.toString();
091
092                int ia = 0;
093                int ib = 0;
094                int nza;
095                int nzb;
096                while (true) {
097                        nza = nzb = 0;
098
099                        char ca = charAt(a, ia);
100                        char cb = charAt(b, ib);
101
102                        while ((isSpaceChar(ca)) || (ca == '0')) {
103                                if (ca == '0') {
104                                        nza++;
105                                } else {
106                                        nza = 0;
107                                }
108
109                                ca = charAt(a, ++ia);
110                        }
111
112                        while ((isSpaceChar(cb)) || (cb == '0')) {
113                                if (cb == '0') {
114                                        nzb++;
115                                } else {
116                                        nzb = 0;
117                                }
118
119                                cb = charAt(b, ++ib);
120                        }
121                        int result;
122                        if ((isDigit(ca)) && (isDigit(cb)) && ((result = compareRight(a.substring(ia), b.substring(ib))) != 0)) {
123                                return result;
124                        }
125
126                        if ((ca == 0) && (cb == 0)) {
127                                return nza - nzb;
128                        }
129
130                        if (ca < cb) {
131                                return -1;
132                        }
133                        if (ca > cb) {
134                                return 1;
135                        }
136
137                        ia++;
138                        ib++;
139                }
140        }
141
142        private static NumberComparator INSTANCE;
143
144        public static NumberComparator getInstance() {
145                if (INSTANCE == null) {
146                        INSTANCE = new NumberComparator();
147                }
148                return INSTANCE;
149        }
150}