    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.Collection;
    024import java.util.Map;
    025import java.util.Set;
    026
    027import org.apache.commons.collections4.IterableMap;
    028import org.apache.commons.collections4.MapIterator;
    029import org.apache.commons.collections4.Unmodifiable;
    030import org.apache.commons.collections4.collection.UnmodifiableCollection;
    031import org.apache.commons.collections4.iterators.EntrySetMapIterator;
    032import org.apache.commons.collections4.iterators.UnmodifiableMapIterator;
    033import org.apache.commons.collections4.set.UnmodifiableSet;
    034
    035/**
    036 * Decorates another {@code Map} to ensure it can't be altered.
    037 * <p>
    038 * This class is Serializable from Commons Collections 3.1.
    039 * </p>
    040 * <p>
    041 * Attempts to modify it will result in an UnsupportedOperationException.
    042 * </p>
    043 *
    044 * @param <K> the type of the keys in this map
    045 * @param <V> the type of the values in this map
    046 * @since 3.0
    047 */
    048public final class UnmodifiableMap<K, V>
    049        extends AbstractMapDecorator<K, V>
    050        implements Unmodifiable, Serializable {
    051
    052    /** Serialization version */
    053    private static final long serialVersionUID = 2737023427269031941L;
    054
    055    /**
    056     * Factory method to create an unmodifiable map.
    057     *
    058     * @param <K>  the key type
    059     * @param <V>  the value type
    060     * @param map  the map to decorate, must not be null
    061     * @return a new unmodifiable map
    062     * @throws NullPointerException if map is null
    063     * @since 4.0
    064     */
    065    public static <K, V> Map<K, V> unmodifiableMap(final Map<? extends K, ? extends V> map) {
    066        if (map instanceof Unmodifiable) {
    067            @SuppressWarnings("unchecked") // safe to upcast
    068            final Map<K, V> tmpMap = (Map<K, V>) map;
    069            return tmpMap;
    070        }
    071        return new UnmodifiableMap<>(map);
    072    }
    073
    074    /**
    075     * Constructor that wraps (not copies).
    076     *
    077     * @param map  the map to decorate, must not be null
    078     * @throws NullPointerException if map is null
    079     */
    080    @SuppressWarnings("unchecked") // safe to upcast
    081    private UnmodifiableMap(final Map<? extends K, ? extends V> map) {
    082        super((Map<K, V>) map);
    083    }
    084
    085    @Override
    086    public void clear() {
    087        throw new UnsupportedOperationException();
    088    }
    089
    090    @Override
    091    public Set<Map.Entry<K, V>> entrySet() {
    092        final Set<Map.Entry<K, V>> set = super.entrySet();
    093        return UnmodifiableEntrySet.unmodifiableEntrySet(set);
    094    }
    095
    096    @Override
    097    public Set<K> keySet() {
    098        final Set<K> set = super.keySet();
    099        return UnmodifiableSet.unmodifiableSet(set);
    100    }
    101
    102    @Override
    103    public MapIterator<K, V> mapIterator() {
    104        if (map instanceof IterableMap) {
    105            final MapIterator<K, V> it = ((IterableMap<K, V>) map).mapIterator();
    106            return UnmodifiableMapIterator.unmodifiableMapIterator(it);
    107        }
    108        final MapIterator<K, V> it = new EntrySetMapIterator<>(map);
    109        return UnmodifiableMapIterator.unmodifiableMapIterator(it);
    110    }
    111
    112    @Override
    113    public V put(final K key, final V value) {
    114        throw new UnsupportedOperationException();
    115    }
    116
    117    @Override
    118    public void putAll(final Map<? extends K, ? extends V> mapToCopy) {
    119        throw new UnsupportedOperationException();
    120    }
    121
    122    /**
    123     * Deserializes the map in using a custom routine.
    124     *
    125     * @param in  the input stream
    126     * @throws IOException if an error occurs while reading from the stream
    127     * @throws ClassNotFoundException if an object read from the stream cannot be loaded
    128     * @since 3.1
    129     */
    130    @SuppressWarnings("unchecked")
    131    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
    132        in.defaultReadObject();
    133        map = (Map<K, V>) in.readObject();
    134    }
    135
    136    @Override
    137    public V remove(final Object key) {
    138        throw new UnsupportedOperationException();
    139    }
    140
    141    @Override
    142    public Collection<V> values() {
    143        final Collection<V> coll = super.values();
    144        return UnmodifiableCollection.unmodifiableCollection(coll);
    145    }
    146
    147    /**
    148     * Serializes this object to an ObjectOutputStream.
    149     *
    150     * @param out the target ObjectOutputStream.
    151     * @throws IOException thrown when an I/O errors occur writing to the target stream.
    152     * @since 3.1
    153     */
    154    private void writeObject(final ObjectOutputStream out) throws IOException {
    155        out.defaultWriteObject();
    156        out.writeObject(map);
    157    }
    158
    159}