hashmaputils.java

一个使用struts+hibernate+spring开发的完的网站源代码。

/*
 * Copyright 2004 The Apache Software Foundation.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.myfaces.util;

import java.util.HashMap;
import java.util.Map;


/**
 * @author Anton Koinov (latest modification by $Author: matze $)
 * @version $Revision: 1.3 $ $Date: 2004/10/13 11:51:01 $
 */
public class HashMapUtils
{
    //~ Constructors -------------------------------------------------------------------------------

    protected HashMapUtils()
    {
        // block public access
    }

    //~ Methods ------------------------------------------------------------------------------------

    /**
     * Calculates initial capacity needed to hold <code>size</code> elements in
     * a HashMap or Hashtable without forcing an expensive increase in internal
     * capacity. Capacity is based on the default load factor of .75.
     * <p>
     * Usage: <code>Map map = new HashMap(HashMapUtils.calcCapacity(10));<code>
     * </p>
     * @param size the number of items that will be put into a HashMap
     * @return initial capacity needed
     */
    public static final int calcCapacity(int size)
    {
        return ((size * 4) + 3) / 3;
    }

    /**
     * Creates a new <code>HashMap</code> that has all of the elements
     * of <code>map1</code> and <code>map2</code> (on key collision, the latter
     * override the former).
     *
     * @param map1 the fist hashmap to merge
     * @param map2 the second hashmap to merge
     * @return new hashmap
     */
    public static HashMap merge(Map map1, Map map2)
    {
        HashMap retval = new HashMap(calcCapacity(map1.size() + map2.size()));

        retval.putAll(map1);
        retval.putAll(map2);

        return retval;
    }
}