ArrayUtils


1   /*
2    * Distributed as part of c3p0 v.0.9.1
3    *
4    * Copyright (C) 2005 Machinery For Change, Inc.
5    *
6    * Author: Steve Waldman <swaldman@mchange.com>
7    *
8    * This library is free software; you can redistribute it and/or modify
9    * it under the terms of the GNU Lesser General Public License version 2.1, as 
10   * published by the Free Software Foundation.
11   *
12   * This software is distributed in the hope that it will be useful,
13   * but WITHOUT ANY WARRANTY; without even the implied warranty of
14   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15   * GNU Lesser General Public License for more details.
16   *
17   * You should have received a copy of the GNU Lesser General Public License
18   * along with this software; see the file LICENSE.  If not, write to the
19   * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
20   * Boston, MA 02111-1307, USA.
21   */
22  
23  
24  package com.mchange.v1.util;
25  
26  import com.mchange.v2.lang.ObjectUtils;
27  
28  public final class ArrayUtils
29  {
30      /**
31       * returns a hash-code for an array consistent with Arrays.equals( ... )
32       */
33      public static int hashArray(Object  [] oo)
34      {
35      int len = oo.length;
36      int out = len;
37      for (int i = 0; i < len; ++i)
38          {
39          //we rotate the bits of the element hashes
40          //around so that the hash has some loaction
41          //dependency
42          int elem_hash = ObjectUtils.hashOrZero(oo[i]);
43          int rot = i % 32;
44          int rot_hash = elem_hash >>> rot;
45          rot_hash |= elem_hash << (32 - rot);
46          out ^= rot_hash;
47          }
48      return out;
49      }
50  
51      /**
52       * returns a hash-code for an array consistent with Arrays.equals( ... )
53       */
54      public static int hashArray(int[] ii)
55      {
56      int len = ii.length;
57      int out = len;
58      for (int i = 0; i < len; ++i)
59          {
60          //we rotate the bits of the element hashes
61          //around so that the hash has some loaction
62          //dependency
63          int elem_hash = ii[i];
64          int rot = i % 32;
65          int rot_hash = elem_hash >>> rot;
66          rot_hash |= elem_hash << (32 - rot);
67          out ^= rot_hash;
68          }
69      return out;
70      }
71  
72      public static int hashOrZeroArray(Object  [] oo)
73      { return (oo == null ? 0 : hashArray(oo)); }
74  
75      public static int hashOrZeroArray(int[] ii)
76      { return (ii == null ? 0 : hashArray(ii)); }
77  
78      public static String   stringifyContents(Object  [] array)
79      {
80      StringBuffer   sb = new StringBuffer  ();
81      sb.append("[ ");
82      for (int i = 0, len = array.length; i < len; ++i)
83          {
84          if (i != 0)
85              sb.append(", ");
86          sb.append( array[i].toString() );
87          }
88      sb.append(" ]");
89      return sb.toString();
90      }
91  }
92  
93
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