    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</code> to ensure it can't be altered.
    037 * <p>
    038 * This class is Serializable from Commons Collections 3.1.
    039 * <p>
    040 * Attempts to modify it will result in an UnsupportedOperationException.
    041 *
    042 * @param <K> the type of the keys in this map
    043 * @param <V> the type of the values in this map
    044 * @since 3.0
    045 */
    046public final class UnmodifiableMap<K, V>
    047        extends AbstractMapDecorator<K, V>
    048        implements Unmodifiable, Serializable {
    049
    050    /** Serialization version */
    051    private static final long serialVersionUID = 2737023427269031941L;
    052
    053    /**
    054     * Factory method to create an unmodifiable map.
    055     *
    056     * @param <K>  the key type
    057     * @param <V>  the value type
    058     * @param map  the map to decorate, must not be null
    059     * @return a new unmodifiable map
    060     * @throws NullPointerException if map is null
    061     * @since 4.0
    062     */
    063    public static <K, V> Map<K, V> unmodifiableMap(final Map<? extends K, ? extends V> map) {
    064        if (map instanceof Unmodifiable) {
    065            @SuppressWarnings("unchecked") // safe to upcast
    066            final Map<K, V> tmpMap = (Map<K, V>) map;
    067            return tmpMap;
    068        }
    069        return new UnmodifiableMap<>(map);
    070    }
    071
    072    //-----------------------------------------------------------------------
    073    /**
    074     * Constructor that wraps (not copies).
    075     *
    076     * @param map  the map to decorate, must not be null
    077     * @throws NullPointerException if map is null
    078     */
    079    @SuppressWarnings("unchecked") // safe to upcast
    080    private UnmodifiableMap(final Map<? extends K, ? extends V> map) {
    081        super((Map<K, V>) map);
    082    }
    083
    084    //-----------------------------------------------------------------------
    085    /**
    086     * Write the map out using a custom routine.
    087     *
    088     * @param out  the output stream
    089     * @throws IOException if an error occurs while writing to the stream
    090     * @since 3.1
    091     */
    092    private void writeObject(final ObjectOutputStream out) throws IOException {
    093        out.defaultWriteObject();
    094        out.writeObject(map);
    095    }
    096
    097    /**
    098     * Read the map in using a custom routine.
    099     *
    100     * @param in  the input stream
    101     * @throws IOException if an error occurs while reading from the stream
    102     * @throws ClassNotFoundException if an object read from the stream can not be loaded
    103     * @since 3.1
    104     */
    105    @SuppressWarnings("unchecked")
    106    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
    107        in.defaultReadObject();
    108        map = (Map<K, V>) in.readObject();
    109    }
    110
    111    //-----------------------------------------------------------------------
    112    @Override
    113    public void clear() {
    114        throw new UnsupportedOperationException();
    115    }
    116
    117    @Override
    118    public V put(final K key, final V value) {
    119        throw new UnsupportedOperationException();
    120    }
    121
    122    @Override
    123    public void putAll(final Map<? extends K, ? extends V> mapToCopy) {
    124        throw new UnsupportedOperationException();
    125    }
    126
    127    @Override
    128    public V remove(final Object key) {
    129        throw new UnsupportedOperationException();
    130    }
    131
    132    @Override
    133    public MapIterator<K, V> mapIterator() {
    134        if (map instanceof IterableMap) {
    135            final MapIterator<K, V> it = ((IterableMap<K, V>) map).mapIterator();
    136            return UnmodifiableMapIterator.unmodifiableMapIterator(it);
    137        }
    138        final MapIterator<K, V> it = new EntrySetMapIterator<>(map);
    139        return UnmodifiableMapIterator.unmodifiableMapIterator(it);
    140    }
    141
    142    @Override
    143    public Set<Map.Entry<K, V>> entrySet() {
    144        final Set<Map.Entry<K, V>> set = super.entrySet();
    145        return UnmodifiableEntrySet.unmodifiableEntrySet(set);
    146    }
    147
    148    @Override
    149    public Set<K> keySet() {
    150        final Set<K> set = super.keySet();
    151        return UnmodifiableSet.unmodifiableSet(set);
    152    }
    153
    154    @Override
    155    public Collection<V> values() {
    156        final Collection<V> coll = super.values();
    157        return UnmodifiableCollection.unmodifiableCollection(coll);
    158    }
    159
    160}