CacheSizes


1   /**
2    * $RCSfile: CacheSizes.java,v $
3    * $Revision: 1.3 $
4    * $Date: 2004/12/26 13:27:16 $
5    *
6    * Copyright (C) 2004 Jive Software. All rights reserved.
7    *
8    * This software is published under the terms of the GNU Public License (GPL),
9    * a copy of which is included in this distribution.
10   */
11  
12  package org.jivesoftware.util;
13  
14  import java.util.Map  ;
15  import java.util.Collection  ;
16  
17  /**
18   * Utility class for determining the sizes in bytes of commonly used objects.
19   * Classes implementing the Cacheable interface should use this class to
20   * determine their size.
21   *
22   * @author Matt Tucker
23   */
24  public class CacheSizes {
25  
26      /**
27       * Returns the size in bytes of a basic Object. This method should only
28       * be used for actual Object objects and not classes that extend Object.
29       *
30       * @return the size of an Object.
31       */
32      public static int sizeOfObject() {
33          return 4;
34      }
35  
36      /**
37       * Returns the size in bytes of a String.
38       *
39       * @param string the String to determine the size of.
40       * @return the size of a String.
41       */
42      public static int sizeOfString(String   string) {
43          if (string == null) {
44              return 0;
45          }
46          return 4 + string.length() * 2;
47      }
48  
49      /**
50       * Returns the size in bytes of a primitive int.
51       *
52       * @return the size of a primitive int.
53       */
54      public static int sizeOfInt() {
55          return 4;
56      }
57  
58      /**
59       * Returns the size in bytes of a primitive char.
60       *
61       * @return the size of a primitive char.
62       */
63      public static int sizeOfChar() {
64          return 2;
65      }
66  
67      /**
68       * Returns the size in bytes of a primitive boolean.
69       *
70       * @return the size of a primitive boolean.
71       */
72      public static int sizeOfBoolean() {
73          return 1;
74      }
75  
76      /**
77       * Returns the size in bytes of a primitive long.
78       *
79       * @return the size of a primitive long.
80       */
81      public static int sizeOfLong() {
82          return 8;
83      }
84  
85      /**
86       * Returns the size in bytes of a primitive double.
87       *
88       * @return the size of a primitive double.
89       */
90      public static int sizeOfDouble() {
91          return 8;
92      }
93  
94      /**
95       * Returns the size in bytes of a Date.
96       *
97       * @return the size of a Date.
98       */
99      public static int sizeOfDate() {
100         return 12;
101     }
102 
103     /**
104      * Returns the size in bytes of a Map object. All keys and
105      * values <b>must be Strings</b>.
106      *
107      * @param map the Map object to determine the size of.
108      * @return the size of the Map object.
109      */
110     public static int sizeOfMap(Map   map) {
111         if (map == null) {
112             return 0;
113         }
114         // Base map object -- should be something around this size.
115         int size = 36;
116         // Add in size of each value
117         Object  [] values = map.values().toArray();
118         for (int i = 0; i < values.length; i++) {
119             size += sizeOfString((String  )values[i]);
120         }
121         Object  [] keys = map.keySet().toArray();
122         // Add in each key
123         for (int i = 0; i < keys.length; i++) {
124             size += sizeOfString((String  )keys[i]);
125         }
126         return size;
127     }
128 
129     /**
130      * Returns the size in bytes of a Collection object. Elements are assumed to be
131      * <tt>String</tt>s, <tt>Long</tt>s or <tt>Cacheable</tt> objects.
132      *
133      * @param list the Collection object to determine the size of.
134      * @return the size of the Collection object.
135      */
136     public static int sizeOfCollection(Collection   list) {
137         if (list == null) {
138             return 0;
139         }
140         // Base list object (approximate)
141         int size = 36;
142         // Add in size of each value
143         Object  [] values = list.toArray();
144         for (int i = 0; i < values.length; i++) {
145             Object   obj = values[i];
146             if (obj instanceof String  ) {
147                 size += sizeOfString((String  )obj);
148             }
149             else if (obj instanceof Long  ) {
150                 size += sizeOfLong() + sizeOfObject();
151             }
152             else {
153                 size += ((Cacheable)obj).getCachedSize();
154             }
155         }
156         return size;
157     }
158 }
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