1   /**
2    * Copyright (c) 2000-2007 Liferay, Inc. All rights reserved.
3    *
4    * Permission is hereby granted, free of charge, to any person obtaining a copy
5    * of this software and associated documentation files (the "Software"), to deal
6    * in the Software without restriction, including without limitation the rights
7    * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
8    * copies of the Software, and to permit persons to whom the Software is
9    * furnished to do so, subject to the following conditions:
10   *
11   * The above copyright notice and this permission notice shall be included in
12   * all copies or substantial portions of the Software.
13   *
14   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
15   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
16   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
17   * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
18   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
19   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
20   * SOFTWARE.
21   */
22  
23  package com.liferay.util;
24  
25  import java.text.NumberFormat;
26  
27  import org.apache.commons.logging.Log;
28  import org.apache.commons.logging.LogFactory;
29  
30  /**
31   * <a href="MathUtil.java.html"><b><i>View Source</i></b></a>
32   *
33   * @author Brian Wing Shun Chan
34   *
35   */
36  public class MathUtil {
37  
38      public static int factorial(int x) {
39          if (x < 0) {
40              return 0;
41          }
42  
43          int factorial = 1;
44  
45          while (x > 1) {
46              factorial = factorial * x;
47              x = x - 1;
48          }
49  
50          return factorial;
51      }
52  
53      public static double format(double x, int max, int min) {
54          NumberFormat nf = NumberFormat.getInstance();
55  
56          nf.setMaximumFractionDigits(max);
57          nf.setMinimumFractionDigits(min);
58  
59          try {
60              Number number = nf.parse(nf.format(x));
61  
62              x = number.doubleValue();
63          }
64          catch (Exception e) {
65              _log.error(e.getMessage());
66          }
67  
68          return x;
69      }
70  
71      public static boolean isEven(int x) {
72          if ((x % 2) == 0) {
73              return true;
74          }
75  
76          return false;
77      }
78  
79      public static boolean isOdd(int x) {
80          return !isEven(x);
81      }
82  
83      public static int[] generatePrimes(int max) {
84          if (max < 2) {
85              return new int[0];
86          }
87          else {
88              boolean[] crossedOut = new boolean[max + 1];
89  
90              for (int i = 2; i < crossedOut.length; i++) {
91                  crossedOut[i] = false;
92              }
93  
94              int limit = (int)Math.sqrt(crossedOut.length);
95  
96              for (int i = 2; i <= limit; i++) {
97                  if (!crossedOut[i]) {
98                      for (int multiple = 2 * i; multiple < crossedOut.length;
99                              multiple += i) {
100 
101                         crossedOut[multiple] = true;
102                     }
103                 }
104             }
105 
106             int uncrossedCount = 0;
107 
108             for (int i = 2; i < crossedOut.length; i++) {
109                 if (!crossedOut[i]) {
110                     uncrossedCount++;
111                 }
112             }
113 
114             int[] result = new int[uncrossedCount];
115 
116             for (int i = 2, j = 0; i < crossedOut.length; i++) {
117                 if (!crossedOut[i]) {
118                     result[j++] = i;
119                 }
120             }
121 
122             return result;
123         }
124     }
125 
126     private static Log _log = LogFactory.getLog(MathUtil.class);
127 
128 }