    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}