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 *      http://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
025/**
026 * A {@code Map} implementation that is a general purpose alternative
027 * to {@code HashMap}.
028 * <p>
029 * This implementation improves on the JDK1.4 HashMap by adding the
030 * {@link org.apache.commons.collections4.MapIterator MapIterator}
031 * functionality and many methods for subclassing.
032 * </p>
033 * <p>
034 * <strong>Note that HashedMap is not synchronized and is not thread-safe.</strong>
035 * If you wish to use this map from multiple threads concurrently, you must use
036 * appropriate synchronization. The simplest approach is to wrap this map
037 * using {@link java.util.Collections#synchronizedMap(Map)}. This class may throw
038 * exceptions when accessed by concurrent threads without synchronization.
039 * </p>
040 *
041 * @param <K> the type of the keys in this map
042 * @param <V> the type of the values in this map
043 * @since 3.0
044 */
045public class HashedMap<K, V>
046        extends AbstractHashedMap<K, V> implements Serializable, Cloneable {
047
048    /** Serialisation version */
049    private static final long serialVersionUID = -1788199231038721040L;
050
051    /**
052     * Constructs a new empty map with default size and load factor.
053     */
054    public HashedMap() {
055        super(DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_THRESHOLD);
056    }
057
058    /**
059     * Constructs a new, empty map with the specified initial capacity.
060     *
061     * @param initialCapacity  the initial capacity
062     * @throws IllegalArgumentException if the initial capacity is negative
063     */
064    public HashedMap(final int initialCapacity) {
065        super(initialCapacity);
066    }
067
068    /**
069     * Constructs a new, empty map with the specified initial capacity and
070     * load factor.
071     *
072     * @param initialCapacity  the initial capacity
073     * @param loadFactor  the load factor
074     * @throws IllegalArgumentException if the initial capacity is negative
075     * @throws IllegalArgumentException if the load factor is less than zero
076     */
077    public HashedMap(final int initialCapacity, final float loadFactor) {
078        super(initialCapacity, loadFactor);
079    }
080
081    /**
082     * Constructor copying elements from another map.
083     *
084     * @param map  the map to copy
085     * @throws NullPointerException if the map is null
086     */
087    public HashedMap(final Map<? extends K, ? extends V> map) {
088        super(map);
089    }
090
091    /**
092     * Clones the map without cloning the keys or values.
093     *
094     * @return a shallow clone
095     */
096    @Override
097    public HashedMap<K, V> clone() {
098        return (HashedMap<K, V>) super.clone();
099    }
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}