    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.Collection;
    024import java.util.Map;
    025import java.util.Set;
    026
    027import org.apache.commons.collections4.BoundedMap;
    028import org.apache.commons.collections4.collection.UnmodifiableCollection;
    029import org.apache.commons.collections4.set.UnmodifiableSet;
    030
    031/**
    032 * Decorates another {@code Map} to fix the size, preventing add/remove.
    033 * <p>
    034 * Any action that would change the size of the map is disallowed.
    035 * The put method is allowed to change the value associated with an existing
    036 * key however.
    037 * </p>
    038 * <p>
    039 * If trying to remove or clear the map, an UnsupportedOperationException is
    040 * thrown. If trying to put a new mapping into the map, an
    041 * IllegalArgumentException is thrown. This is because the put method can
    042 * succeed if the mapping's key already exists in the map, so the put method
    043 * is not always unsupported.
    044 * </p>
    045 * <p>
    046 * <strong>Note that FixedSizeMap is not synchronized and is not thread-safe.</strong>
    047 * If you wish to use this map from multiple threads concurrently, you must use
    048 * appropriate synchronization. The simplest approach is to wrap this map
    049 * using {@link java.util.Collections#synchronizedMap(Map)}. This class may throw
    050 * exceptions when accessed by concurrent threads without synchronization.
    051 * </p>
    052 * <p>
    053 * This class is Serializable from Commons Collections 3.1.
    054 * </p>
    055 *
    056 * @param <K> The type of the keys in this map
    057 * @param <V> The type of the values in this map
    058 * @since 3.0
    059 */
    060public class FixedSizeMap<K, V>
    061        extends AbstractMapDecorator<K, V>
    062        implements BoundedMap<K, V>, Serializable {
    063
    064    /** Serialization version */
    065    private static final long serialVersionUID = 7450927208116179316L;
    066
    067    /**
    068     * Factory method to create a fixed size map.
    069     *
    070     * @param <K>  the key type
    071     * @param <V>  the value type
    072     * @param map  The map to decorate, must not be null
    073     * @return A new fixed size map
    074     * @throws NullPointerException if map is null
    075     * @since 4.0
    076     */
    077    public static <K, V> FixedSizeMap<K, V> fixedSizeMap(final Map<K, V> map) {
    078        return new FixedSizeMap<>(map);
    079    }
    080
    081    /**
    082     * Constructor that wraps (not copies).
    083     *
    084     * @param map  The map to decorate, must not be null
    085     * @throws NullPointerException if map is null
    086     */
    087    protected FixedSizeMap(final Map<K, V> map) {
    088        super(map);
    089    }
    090
    091    /**
    092     * Always throws {@link UnsupportedOperationException}.
    093     *
    094     * @throws UnsupportedOperationException Always thrown.
    095     */
    096    @Override
    097    public void clear() {
    098        throw new UnsupportedOperationException("Map is fixed size");
    099    }
    100
    101    @Override
    102    public Set<Map.Entry<K, V>> entrySet() {
    103        final Set<Map.Entry<K, V>> set = map.entrySet();
    104        // unmodifiable set will still allow modification via Map.Entry objects
    105        return UnmodifiableSet.unmodifiableSet(set);
    106    }
    107
    108    @Override
    109    public boolean isFull() {
    110        return true;
    111    }
    112
    113    @Override
    114    public Set<K> keySet() {
    115        final Set<K> set = map.keySet();
    116        return UnmodifiableSet.unmodifiableSet(set);
    117    }
    118
    119    @Override
    120    public int maxSize() {
    121        return size();
    122    }
    123
    124    @Override
    125    public V put(final K key, final V value) {
    126        if (!map.containsKey(key)) {
    127            throw new IllegalArgumentException("Cannot put new key/value pair - Map is fixed size");
    128        }
    129        return map.put(key, value);
    130    }
    131
    132    @Override
    133    public void putAll(final Map<? extends K, ? extends V> mapToCopy) {
    134        for (final K key : mapToCopy.keySet()) {
    135            if (!containsKey(key)) {
    136                throw new IllegalArgumentException("Cannot put new key/value pair - Map is fixed size");
    137            }
    138        }
    139        map.putAll(mapToCopy);
    140    }
    141
    142    /**
    143     * Deserializes the map in using a custom routine.
    144     *
    145     * @param in  The input stream
    146     * @throws IOException Thrown if an error occurs while reading from the stream
    147     * @throws ClassNotFoundException if an object read from the stream cannot be loaded
    148     * @since 3.1
    149     */
    150    @SuppressWarnings("unchecked") // (1) should only fail if input stream is incorrect
    151    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
    152        in.defaultReadObject();
    153        map = (Map<K, V>) in.readObject(); // (1)
    154    }
    155
    156    /**
    157     * Always throws {@link UnsupportedOperationException}.
    158     *
    159     * @param key Ignored.
    160     * @throws UnsupportedOperationException Always thrown.
    161     */
    162    @Override
    163    public V remove(final Object key) {
    164        throw new UnsupportedOperationException("Map is fixed size");
    165    }
    166
    167    @Override
    168    public Collection<V> values() {
    169        return UnmodifiableCollection.unmodifiableCollection(map.values());
    170    }
    171
    172    /**
    173     * Serializes this object to an ObjectOutputStream.
    174     *
    175     * @param out The target ObjectOutputStream.
    176     * @throws IOException thrown when an I/O errors occur writing to the target stream.
    177     * @since 3.1
    178     */
    179    private void writeObject(final ObjectOutputStream out) throws IOException {
    180        out.defaultWriteObject();
    181        out.writeObject(map);
    182    }
    183
    184}