001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      https://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.collections4.map;
018
019import java.io.IOException;
020import java.io.ObjectInputStream;
021import java.io.ObjectOutputStream;
022import java.io.Serializable;
023import java.util.Map;
024
025import org.apache.commons.collections4.MapIterator;
026
027/**
028 * A {@code Map} implementation that is a general purpose alternative
029 * to {@code HashMap}.
030 * <p>
031 * This implementation improves on the JDK1.4 HashMap by adding the
032 * {@link MapIterator MapIterator}
033 * functionality and many methods for subclassing.
034 * </p>
035 * <p>
036 * <strong>Note that HashedMap is not synchronized and is not thread-safe.</strong>
037 * If you wish to use this map from multiple threads concurrently, you must use
038 * appropriate synchronization. The simplest approach is to wrap this map
039 * using {@link java.util.Collections#synchronizedMap(Map)}. This class may throw
040 * exceptions when accessed by concurrent threads without synchronization.
041 * </p>
042 *
043 * @param <K> The type of the keys in this map
044 * @param <V> The type of the values in this map
045 * @since 3.0
046 */
047public class HashedMap<K, V>
048        extends AbstractHashedMap<K, V> implements Serializable, Cloneable {
049
050    /** Serialization version */
051    private static final long serialVersionUID = -1788199231038721040L;
052
053    /**
054     * Constructs a new empty map with default size and load factor.
055     */
056    public HashedMap() {
057        super(DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_THRESHOLD);
058    }
059
060    /**
061     * Constructs a new, empty map with the specified initial capacity.
062     *
063     * @param initialCapacity  The initial capacity
064     * @throws IllegalArgumentException if the initial capacity is negative
065     */
066    public HashedMap(final int initialCapacity) {
067        super(initialCapacity);
068    }
069
070    /**
071     * Constructs a new, empty map with the specified initial capacity and
072     * load factor.
073     *
074     * @param initialCapacity  The initial capacity
075     * @param loadFactor  The load factor
076     * @throws IllegalArgumentException if the initial capacity is negative
077     * @throws IllegalArgumentException if the load factor is less than zero
078     */
079    public HashedMap(final int initialCapacity, final float loadFactor) {
080        super(initialCapacity, loadFactor);
081    }
082
083    /**
084     * Constructor copying elements from another map.
085     *
086     * @param map  The map to copy
087     * @throws NullPointerException if the map is null
088     */
089    public HashedMap(final Map<? extends K, ? extends V> map) {
090        super(map);
091    }
092
093    /**
094     * Clones the map without cloning the keys or values.
095     *
096     * @return A shallow clone
097     */
098    @Override
099    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}