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 * https://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 import org.apache.commons.collections4.MapIterator;
26
27 /**
28 * A {@code Map} implementation that is a general purpose alternative
29 * to {@code HashMap}.
30 * <p>
31 * This implementation improves on the JDK1.4 HashMap by adding the
32 * {@link MapIterator MapIterator}
33 * functionality and many methods for subclassing.
34 * </p>
35 * <p>
36 * <strong>Note that HashedMap is not synchronized and is not thread-safe.</strong>
37 * If you wish to use this map from multiple threads concurrently, you must use
38 * appropriate synchronization. The simplest approach is to wrap this map
39 * using {@link java.util.Collections#synchronizedMap(Map)}. This class may throw
40 * exceptions when accessed by concurrent threads without synchronization.
41 * </p>
42 *
43 * @param <K> The type of the keys in this map
44 * @param <V> The type of the values in this map
45 * @since 3.0
46 */
47 public class HashedMap<K, V>
48 extends AbstractHashedMap<K, V> implements Serializable, Cloneable {
49
50 /** Serialization version */
51 private static final long serialVersionUID = -1788199231038721040L;
52
53 /**
54 * Constructs a new empty map with default size and load factor.
55 */
56 public HashedMap() {
57 super(DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_THRESHOLD);
58 }
59
60 /**
61 * Constructs a new, empty map with the specified initial capacity.
62 *
63 * @param initialCapacity The initial capacity
64 * @throws IllegalArgumentException if the initial capacity is negative
65 */
66 public HashedMap(final int initialCapacity) {
67 super(initialCapacity);
68 }
69
70 /**
71 * Constructs a new, empty map with the specified initial capacity and
72 * load factor.
73 *
74 * @param initialCapacity The initial capacity
75 * @param loadFactor The load factor
76 * @throws IllegalArgumentException if the initial capacity is negative
77 * @throws IllegalArgumentException if the load factor is less than zero
78 */
79 public HashedMap(final int initialCapacity, final float loadFactor) {
80 super(initialCapacity, loadFactor);
81 }
82
83 /**
84 * Constructor copying elements from another map.
85 *
86 * @param map The map to copy
87 * @throws NullPointerException if the map is null
88 */
89 public HashedMap(final Map<? extends K, ? extends V> map) {
90 super(map);
91 }
92
93 /**
94 * Clones the map without cloning the keys or values.
95 *
96 * @return A shallow clone
97 */
98 @Override
99 public HashedMap<K, V> clone() {
100 return (HashedMap<K, V>) super.clone();
101 }
102
103 /**
104 * Deserializes the map in using a custom routine.
105 *
106 * @param in The input stream
107 * @throws IOException Thrown if an error occurs while reading from the stream
108 * @throws ClassNotFoundException if an object read from the stream cannot be loaded
109 */
110 private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
111 in.defaultReadObject();
112 doReadObject(in);
113 }
114
115 /**
116 * Serializes this object to an ObjectOutputStream.
117 *
118 * @param out The target ObjectOutputStream.
119 * @throws IOException thrown when an I/O errors occur writing to the target stream.
120 */
121 private void writeObject(final ObjectOutputStream out) throws IOException {
122 out.defaultWriteObject();
123 doWriteObject(out);
124 }
125
126 }