001    /**
002     * Copyright (c) 2000-present Liferay, Inc. All rights reserved.
003     *
004     * This library is free software; you can redistribute it and/or modify it under
005     * the terms of the GNU Lesser General Public License as published by the Free
006     * Software Foundation; either version 2.1 of the License, or (at your option)
007     * any later version.
008     *
009     * This library is distributed in the hope that it will be useful, but WITHOUT
010     * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
011     * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
012     * details.
013     */
014    
015    package com.liferay.portal.kernel.util;
016    
017    import com.liferay.portal.kernel.log.Log;
018    import com.liferay.portal.kernel.log.LogFactoryUtil;
019    
020    import java.text.NumberFormat;
021    
022    import java.util.HashMap;
023    import java.util.Map;
024    
025    /**
026     * @author Brian Wing Shun Chan
027     */
028    public class MathUtil {
029    
030            public static int base2Log(long x) {
031                    return _base2LogValues.get(x);
032            }
033    
034            public static long base2Pow(int x) {
035                    if (x == 0) {
036                            return 1;
037                    }
038                    else {
039                            return 2L << (x - 1);
040                    }
041            }
042    
043            public static int difference(Integer value1, Integer value2) {
044                    return value1 - value2;
045            }
046    
047            public static int factorial(int x) {
048                    if (x < 0) {
049                            return 0;
050                    }
051    
052                    int factorial = 1;
053    
054                    while (x > 1) {
055                            factorial = factorial * x;
056                            x = x - 1;
057                    }
058    
059                    return factorial;
060            }
061    
062            public static double format(double x, int max, int min) {
063                    NumberFormat nf = NumberFormat.getInstance();
064    
065                    nf.setMaximumFractionDigits(max);
066                    nf.setMinimumFractionDigits(min);
067    
068                    try {
069                            Number number = nf.parse(nf.format(x));
070    
071                            x = number.doubleValue();
072                    }
073                    catch (Exception e) {
074                            _log.error(e.getMessage());
075                    }
076    
077                    return x;
078            }
079    
080            public static int[] generatePrimes(int max) {
081                    if (max < 2) {
082                            return new int[0];
083                    }
084    
085                    boolean[] crossedOut = new boolean[max + 1];
086    
087                    for (int i = 2; i < crossedOut.length; i++) {
088                            crossedOut[i] = false;
089                    }
090    
091                    int limit = (int)Math.sqrt(crossedOut.length);
092    
093                    for (int i = 2; i <= limit; i++) {
094                            if (!crossedOut[i]) {
095                                    for (int multiple = 2 * i; multiple < crossedOut.length;
096                                                    multiple += i) {
097    
098                                            crossedOut[multiple] = true;
099                                    }
100                            }
101                    }
102    
103                    int uncrossedCount = 0;
104    
105                    for (int i = 2; i < crossedOut.length; i++) {
106                            if (!crossedOut[i]) {
107                                    uncrossedCount++;
108                            }
109                    }
110    
111                    int[] result = new int[uncrossedCount];
112    
113                    for (int i = 2, j = 0; i < crossedOut.length; i++) {
114                            if (!crossedOut[i]) {
115                                    result[j++] = i;
116                            }
117                    }
118    
119                    return result;
120            }
121    
122            public static boolean isEven(int x) {
123                    if ((x % 2) == 0) {
124                            return true;
125                    }
126    
127                    return false;
128            }
129    
130            public static boolean isOdd(int x) {
131                    return !isEven(x);
132            }
133    
134            public static double product(Double... values) {
135                    double product = 1.0;
136    
137                    for (double value : values) {
138                            product *= value;
139                    }
140    
141                    return product;
142            }
143    
144            public static int product(Integer... values) {
145                    int product = 1;
146    
147                    for (int value : values) {
148                            product *= value;
149                    }
150    
151                    return product;
152            }
153    
154            public static long product(Long... values) {
155                    long product = 1;
156    
157                    for (long value : values) {
158                            product *= value;
159                    }
160    
161                    return product;
162            }
163    
164            public static int quotient(Integer value1, Integer value2) {
165                    return value1 / value2;
166            }
167    
168            public static double sum(Double... values) {
169                    double sum = 0.0;
170    
171                    for (double value : values) {
172                            sum += value;
173                    }
174    
175                    return sum;
176            }
177    
178            public static int sum(Integer... values) {
179                    int sum = 0;
180    
181                    for (int value : values) {
182                            sum += value;
183                    }
184    
185                    return sum;
186            }
187    
188            public static long sum(Long... values) {
189                    long sum = 0;
190    
191                    for (long value : values) {
192                            sum += value;
193                    }
194    
195                    return sum;
196            }
197    
198            private static final Log _log = LogFactoryUtil.getLog(MathUtil.class);
199    
200            private static final Map<Long, Integer> _base2LogValues = new HashMap<>();
201    
202            static {
203                    _base2LogValues.put(0L, Integer.MIN_VALUE);
204    
205                    for (int i = 0; i < 63; i++) {
206                            _base2LogValues.put(base2Pow(i), i);
207                    }
208            }
209    
210    }