1   /**
2    * Copyright (c) 2000-2009 Liferay, Inc. All rights reserved.
3    *
4    * The contents of this file are subject to the terms of the Liferay Enterprise
5    * Subscription License ("License"). You may not use this file except in
6    * compliance with the License. You can obtain a copy of the License by
7    * contacting Liferay, Inc. See the License for the specific language governing
8    * permissions and limitations under the License, including but not limited to
9    * distribution rights of the Software.
10   *
11   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
12   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
13   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
14   * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
15   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
16   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
17   * SOFTWARE.
18   */
19  
20  package com.liferay.portal.kernel.util;
21  
22  import com.liferay.portal.kernel.log.Log;
23  import com.liferay.portal.kernel.log.LogFactoryUtil;
24  
25  import java.text.NumberFormat;
26  
27  import java.util.HashMap;
28  import java.util.Map;
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 base2Log(long x) {
39          return _base2LogValues.get(x);
40      }
41  
42      public static long base2Pow(int x) {
43          if (x == 0) {
44              return 1;
45          }
46          else {
47              return 2L << (x - 1);
48          }
49      }
50  
51      public static int factorial(int x) {
52          if (x < 0) {
53              return 0;
54          }
55  
56          int factorial = 1;
57  
58          while (x > 1) {
59              factorial = factorial * x;
60              x = x - 1;
61          }
62  
63          return factorial;
64      }
65  
66      public static double format(double x, int max, int min) {
67          NumberFormat nf = NumberFormat.getInstance();
68  
69          nf.setMaximumFractionDigits(max);
70          nf.setMinimumFractionDigits(min);
71  
72          try {
73              Number number = nf.parse(nf.format(x));
74  
75              x = number.doubleValue();
76          }
77          catch (Exception e) {
78              _log.error(e.getMessage());
79          }
80  
81          return x;
82      }
83  
84      public static boolean isEven(int x) {
85          if ((x % 2) == 0) {
86              return true;
87          }
88  
89          return false;
90      }
91  
92      public static boolean isOdd(int x) {
93          return !isEven(x);
94      }
95  
96      public static int[] generatePrimes(int max) {
97          if (max < 2) {
98              return new int[0];
99          }
100         else {
101             boolean[] crossedOut = new boolean[max + 1];
102 
103             for (int i = 2; i < crossedOut.length; i++) {
104                 crossedOut[i] = false;
105             }
106 
107             int limit = (int)Math.sqrt(crossedOut.length);
108 
109             for (int i = 2; i <= limit; i++) {
110                 if (!crossedOut[i]) {
111                     for (int multiple = 2 * i; multiple < crossedOut.length;
112                             multiple += i) {
113 
114                         crossedOut[multiple] = true;
115                     }
116                 }
117             }
118 
119             int uncrossedCount = 0;
120 
121             for (int i = 2; i < crossedOut.length; i++) {
122                 if (!crossedOut[i]) {
123                     uncrossedCount++;
124                 }
125             }
126 
127             int[] result = new int[uncrossedCount];
128 
129             for (int i = 2, j = 0; i < crossedOut.length; i++) {
130                 if (!crossedOut[i]) {
131                     result[j++] = i;
132                 }
133             }
134 
135             return result;
136         }
137     }
138 
139     private static Log _log = LogFactoryUtil.getLog(MathUtil.class);
140 
141     private static Map<Long, Integer> _base2LogValues =
142         new HashMap<Long, Integer>();
143 
144     static {
145         _base2LogValues.put(0L, Integer.MIN_VALUE);
146 
147         for (int i = 0; i < 63; i++) {
148             _base2LogValues.put(base2Pow(i), i);
149         }
150     }
151 
152 }