1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 */
19 package org.apache.myfaces.shared.util;
20
21 import java.util.HashMap;
22 import java.util.Map;
23 import java.util.Set;
24 import java.util.Iterator;
25
26
27 public class HashMapUtils
28 {
29 //~ Constructors -------------------------------------------------------------------------------
30
31 protected HashMapUtils()
32 {
33 // block public access
34 }
35
36 //~ Methods ------------------------------------------------------------------------------------
37
38 /**
39 * Calculates initial capacity needed to hold <code>size</code> elements in
40 * a HashMap or Hashtable without forcing an expensive increase in internal
41 * capacity. Capacity is based on the default load factor of .75.
42 * <p>
43 * Usage: <code>Map map = new HashMap(HashMapUtils.calcCapacity(10));<code>
44 * </p>
45 * @param size the number of items that will be put into a HashMap
46 * @return initial capacity needed
47 */
48 public static final int calcCapacity(int size)
49 {
50 return ((size * 4) + 3) / 3;
51 }
52
53 /**
54 * Creates a new <code>HashMap</code> that has all of the elements
55 * of <code>map1</code> and <code>map2</code> (on key collision, the latter
56 * override the former).
57 *
58 * @param map1 the fist hashmap to merge
59 * @param map2 the second hashmap to merge
60 * @return new hashmap
61 */
62 public static HashMap merge(Map map1, Map map2)
63 {
64 HashMap retval = new HashMap(calcCapacity(map1.size() + map2.size()));
65
66 retval.putAll(map1);
67 retval.putAll(map2);
68
69 return retval;
70 }
71
72 /**
73 * spit out each name/value pair
74 */
75 public static String mapToString(Map map)
76 {
77 Set entries = map.entrySet();
78 Iterator iter = entries.iterator();
79 StringBuffer buff = new StringBuffer();
80 while (iter.hasNext())
81 {
82 Map.Entry entry = (Map.Entry) iter.next();
83 buff.append("[" + entry.getKey() + "," + entry.getValue() + "]\n");
84 }
85 return buff.toString();
86 }
87
88 }