1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.collections4.map;
18
19 import java.io.IOException;
20 import java.io.ObjectInputStream;
21 import java.io.ObjectOutputStream;
22 import java.io.Serializable;
23 import java.util.Map;
24
25 /**
26 * A {@code Map} implementation that is a general purpose alternative
27 * to {@code HashMap}.
28 * <p>
29 * This implementation improves on the JDK1.4 HashMap by adding the
30 * {@link org.apache.commons.collections4.MapIterator MapIterator}
31 * functionality and many methods for subclassing.
32 * </p>
33 * <p>
34 * <strong>Note that HashedMap is not synchronized and is not thread-safe.</strong>
35 * If you wish to use this map from multiple threads concurrently, you must use
36 * appropriate synchronization. The simplest approach is to wrap this map
37 * using {@link java.util.Collections#synchronizedMap(Map)}. This class may throw
38 * exceptions when accessed by concurrent threads without synchronization.
39 * </p>
40 *
41 * @param <K> the type of the keys in this map
42 * @param <V> the type of the values in this map
43 * @since 3.0
44 */
45 public class HashedMap<K, V>
46 extends AbstractHashedMap<K, V> implements Serializable, Cloneable {
47
48 /** Serialisation version */
49 private static final long serialVersionUID = -1788199231038721040L;
50
51 /**
52 * Constructs a new empty map with default size and load factor.
53 */
54 public HashedMap() {
55 super(DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_THRESHOLD);
56 }
57
58 /**
59 * Constructs a new, empty map with the specified initial capacity.
60 *
61 * @param initialCapacity the initial capacity
62 * @throws IllegalArgumentException if the initial capacity is negative
63 */
64 public HashedMap(final int initialCapacity) {
65 super(initialCapacity);
66 }
67
68 /**
69 * Constructs a new, empty map with the specified initial capacity and
70 * load factor.
71 *
72 * @param initialCapacity the initial capacity
73 * @param loadFactor the load factor
74 * @throws IllegalArgumentException if the initial capacity is negative
75 * @throws IllegalArgumentException if the load factor is less than zero
76 */
77 public HashedMap(final int initialCapacity, final float loadFactor) {
78 super(initialCapacity, loadFactor);
79 }
80
81 /**
82 * Constructor copying elements from another map.
83 *
84 * @param map the map to copy
85 * @throws NullPointerException if the map is null
86 */
87 public HashedMap(final Map<? extends K, ? extends V> map) {
88 super(map);
89 }
90
91 /**
92 * Clones the map without cloning the keys or values.
93 *
94 * @return a shallow clone
95 */
96 @Override
97 public HashedMap<K, V> clone() {
98 return (HashedMap<K, V>) super.clone();
99 }
100
101 /**
102 * Read the map in using a custom routine.
103 *
104 * @param in the input stream
105 * @throws IOException if an error occurs while reading from the stream
106 * @throws ClassNotFoundException if an object read from the stream can not be loaded
107 */
108 private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
109 in.defaultReadObject();
110 doReadObject(in);
111 }
112
113 /**
114 * Write the map out using a custom routine.
115 *
116 * @param out the output stream
117 * @throws IOException if an error occurs while writing to the stream
118 */
119 private void writeObject(final ObjectOutputStream out) throws IOException {
120 out.defaultWriteObject();
121 doWriteObject(out);
122 }
123
124 }