com.ejoysoft.util.CacheSizes.java Source code

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Here is the source code for com.ejoysoft.util.CacheSizes.java

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/**
 * $RCSfile: CacheSizes.java,v $
 * $Revision: 1.1.1.1 $
 * $Date: 2002/09/09 13:51:09 $
 *
 * New Jive  from Jdon.com.
 *
 * This software is the proprietary information of CoolServlets, Inc.
 * Use is subject to license terms.
 */

package com.ejoysoft.util;

import java.util.*;
import java.lang.reflect.Field;

import org.apache.commons.logging.LogFactory;
import org.apache.commons.logging.Log;

/**
 * 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.
 */
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 Properties object. All properties and
     * property names must be Strings.
     *
     * @param properties the Properties object to determine the size of.
     * @return the size of a Properties object.
     */

    /**
     * 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
        Iterator iter = map.values().iterator();
        while (iter.hasNext()) {
            String value = (String) iter.next();
            size += sizeOfString(value);
        }
        //Add in each key
        iter = map.keySet().iterator();
        while (iter.hasNext()) {
            String key = (String) iter.next();
            size += sizeOfString(key);
        }
        return size;
    }

    /**
     * Returns the size in bytes of a List object. All elements
     * <b>must be Strings</b>.
     *
     * @param list the List object to determine the size of.
     * @return the size of the List object.
     */
    public static int sizeOfList(List list) {
        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++) {
            size += sizeOfString((String) values[i]);
        }
        return size;
    }

    private static Log logger = LogFactory.getLog(CacheSizes.class);

    public static long cacheSizeOfObject(Object bean) {

        // Approximate the size of the object in bytes by calculating the size
        // of each field.
        Field[] fields = bean.getClass().getDeclaredFields();
        long size = CacheSizes.sizeOfObject();

        return size;
    }

}