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Java > Open Source Codes > org > shiftone > cache > util > MapFactory


1 package org.shiftone.cache.util;
2
3
4
5 import java.util.Arrays JavaDoc;
6 import java.util.Hashtable JavaDoc;
7 import java.util.Map JavaDoc;
8
9
10 /**
11  * @version $Revision: 1.4 $
12  * @author <a HREF="mailto:jeff@shiftone.org">Jeff Drost</a>
13  */
14 public class MapFactory
15 {
16
17     private static final Log LOG = new Log(MapFactory.class);
18     public static final float DEFAULT_LOAD_FACTOR = 0.5f;
19     public static final int[] PRIMES =
20     {
21
22         // 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 37, 43, 53, 59, 67, 79, 89, 101, 113, 127, 149, //
23 167, 191, 223, 251, 281, 313, 349, 389, 433, 487, 541, 601, 673, 751, 839, 937, 1049, //
24 1171, 1301, 1447, 1607, 1787, 1987, 2207, 2459, 2731, 3037, 3373, 3761, 4177, 4637, //
25 5153, 5737, 6373, 7079, 7867, 8737, 9719, 10789, 11981, 13309, 14779, 16411, 18217, //
26 20231, 22469, 24943, 27689, 30757, 34141, 37897, 42071, 46703, 51853, 57557, 63901, //
27 70937, 78779, 87473, 97103, 107791, 119653, 132817, 147449, 163673, 181693, 201683, //
28 223903, 248533, 275881, 306239, 339943, 377339, 418849, 464923, 516077, 572867, 635891, //
29 705841, 783487, 869683, 965357, 1071563, 1189453, 1320301, 1465547, 1626763, 1805729, //
30 2004377, 2224861, 2469629, 2741303, 3042857, 3377579, 3749117, 4161527, 4619309, //
31 5127433, 5691457, 6317527, 7012469, 7783843, 8640109, 9590531, 10645507, 11816521, //
32 13116343, 14559151, 16160663, 17938357, 19911581, 22101889, 24533099, 27231751, //
33 30227287, 33552293, 37243051, 41339843, Integer.MAX_VALUE
34     };
35
36     public static int getNearPrime(int number)
37     {
38
39         int value = Arrays.binarySearch(PRIMES, number);
40
41         if (value < 0)
42         {
43             value = -value - 1;
44         }
45
46         return PRIMES[value];
47     }
48
49
50     public static Map JavaDoc createMap(int initialCapacity)
51     {
52         return new Hashtable JavaDoc(getNearPrime(initialCapacity), DEFAULT_LOAD_FACTOR);
53     }
54
55
56     private static void test(int a)
57     {
58
59         int b = getNearPrime(a);
60
61         LOG.info(a + " -> " + b);
62     }
63
64
65     public static void main(String JavaDoc args[])
66     {
67
68         test(0);
69         test(965356);
70         test(965357);
71         test(965358);
72         test(Integer.MAX_VALUE);
73     }
74 }
75
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