CacheSizes.java 3.99 KB
Newer Older
1
/**
Matt Tucker's avatar
Matt Tucker committed
2 3 4 5
 * $RCSfile$
 * $Revision$
 * $Date$
 *
6
 * Copyright (C) 2004 Jive Software. All rights reserved.
Matt Tucker's avatar
Matt Tucker committed
7
 *
8 9
 * This software is published under the terms of the GNU Public License (GPL),
 * a copy of which is included in this distribution.
Matt Tucker's avatar
Matt Tucker committed
10 11 12 13 14
 */

package org.jivesoftware.util;

import java.util.Map;
15
import java.util.Collection;
Matt Tucker's avatar
Matt Tucker committed
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129

/**
 * Utility class for determining the sizes in bytes of commonly used objects.
 * Classes implementing the Cacheable interface should use this class to
 * determine their size.
 *
 * @author Matt Tucker
 */
public class CacheSizes {

    /**
     * Returns the size in bytes of a basic Object. This method should only
     * be used for actual Object objects and not classes that extend Object.
     *
     * @return the size of an Object.
     */
    public static int sizeOfObject() {
        return 4;
    }

    /**
     * Returns the size in bytes of a String.
     *
     * @param string the String to determine the size of.
     * @return the size of a String.
     */
    public static int sizeOfString(String string) {
        if (string == null) {
            return 0;
        }
        return 4 + string.length() * 2;
    }

    /**
     * Returns the size in bytes of a primitive int.
     *
     * @return the size of a primitive int.
     */
    public static int sizeOfInt() {
        return 4;
    }

    /**
     * Returns the size in bytes of a primitive char.
     *
     * @return the size of a primitive char.
     */
    public static int sizeOfChar() {
        return 2;
    }

    /**
     * Returns the size in bytes of a primitive boolean.
     *
     * @return the size of a primitive boolean.
     */
    public static int sizeOfBoolean() {
        return 1;
    }

    /**
     * Returns the size in bytes of a primitive long.
     *
     * @return the size of a primitive long.
     */
    public static int sizeOfLong() {
        return 8;
    }

    /**
     * Returns the size in bytes of a primitive double.
     *
     * @return the size of a primitive double.
     */
    public static int sizeOfDouble() {
        return 8;
    }

    /**
     * Returns the size in bytes of a Date.
     *
     * @return the size of a Date.
     */
    public static int sizeOfDate() {
        return 12;
    }

    /**
     * Returns the size in bytes of a Map object. All keys and
     * values <b>must be Strings</b>.
     *
     * @param map the Map object to determine the size of.
     * @return the size of the Map object.
     */
    public static int sizeOfMap(Map map) {
        if (map == null) {
            return 0;
        }
        // Base map object -- should be something around this size.
        int size = 36;
        // Add in size of each value
        Object[] values = map.values().toArray();
        for (int i = 0; i < values.length; i++) {
            size += sizeOfString((String)values[i]);
        }
        Object[] keys = map.keySet().toArray();
        // Add in each key
        for (int i = 0; i < keys.length; i++) {
            size += sizeOfString((String)keys[i]);
        }
        return size;
    }

    /**
130
     * Returns the size in bytes of a Collection object. Elements are assumed to be
Matt Tucker's avatar
Matt Tucker committed
131 132
     * <tt>String</tt>s, <tt>Long</tt>s or <tt>Cacheable</tt> objects.
     *
133 134
     * @param list the Collection object to determine the size of.
     * @return the size of the Collection object.
Matt Tucker's avatar
Matt Tucker committed
135
     */
136
    public static int sizeOfCollection(Collection list) {
Matt Tucker's avatar
Matt Tucker committed
137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158
        if (list == null) {
            return 0;
        }
        // Base list object (approximate)
        int size = 36;
        // Add in size of each value
        Object[] values = list.toArray();
        for (int i = 0; i < values.length; i++) {
            Object obj = values[i];
            if (obj instanceof String) {
                size += sizeOfString((String)obj);
            }
            else if (obj instanceof Long) {
                size += sizeOfLong() + sizeOfObject();
            }
            else {
                size += ((Cacheable)obj).getCachedSize();
            }
        }
        return size;
    }
}