    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}