    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.BoundedMap;
    028import org.apache.commons.collections4.collection.UnmodifiableCollection;
    029import org.apache.commons.collections4.set.UnmodifiableSet;
    030
    031/**
    032 * Decorates another <code>Map</code> 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    /**
    083     * Constructor that wraps (not copies).
    084     *
    085     * @param map  the map to decorate, must not be null
    086     * @throws NullPointerException if map is null
    087     */
    088    protected FixedSizeMap(final Map<K, V> map) {
    089        super(map);
    090    }
    091
    092    //-----------------------------------------------------------------------
    093    /**
    094     * Write the map out using a custom routine.
    095     *
    096     * @param out  the output stream
    097     * @throws IOException if an error occurs while writing to the stream
    098     * @since 3.1
    099     */
    100    private void writeObject(final ObjectOutputStream out) throws IOException {
    101        out.defaultWriteObject();
    102        out.writeObject(map);
    103    }
    104
    105    /**
    106     * Read the map in using a custom routine.
    107     *
    108     * @param in  the input stream
    109     * @throws IOException if an error occurs while reading from the stream
    110     * @throws ClassNotFoundException if an object read from the stream can not be loaded
    111     * @since 3.1
    112     */
    113    @SuppressWarnings("unchecked") // (1) should only fail if input stream is incorrect
    114    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
    115        in.defaultReadObject();
    116        map = (Map<K, V>) in.readObject(); // (1)
    117    }
    118
    119    //-----------------------------------------------------------------------
    120    @Override
    121    public V put(final K key, final V value) {
    122        if (map.containsKey(key) == false) {
    123            throw new IllegalArgumentException("Cannot put new key/value pair - Map is fixed size");
    124        }
    125        return map.put(key, value);
    126    }
    127
    128    @Override
    129    public void putAll(final Map<? extends K, ? extends V> mapToCopy) {
    130        for (final K key : mapToCopy.keySet()) {
    131            if (!containsKey(key)) {
    132                throw new IllegalArgumentException("Cannot put new key/value pair - Map is fixed size");
    133            }
    134        }
    135        map.putAll(mapToCopy);
    136    }
    137
    138    @Override
    139    public void clear() {
    140        throw new UnsupportedOperationException("Map is fixed size");
    141    }
    142
    143    @Override
    144    public V remove(final Object key) {
    145        throw new UnsupportedOperationException("Map is fixed size");
    146    }
    147
    148    @Override
    149    public Set<Map.Entry<K, V>> entrySet() {
    150        final Set<Map.Entry<K, V>> set = map.entrySet();
    151        // unmodifiable set will still allow modification via Map.Entry objects
    152        return UnmodifiableSet.unmodifiableSet(set);
    153    }
    154
    155    @Override
    156    public Set<K> keySet() {
    157        final Set<K> set = map.keySet();
    158        return UnmodifiableSet.unmodifiableSet(set);
    159    }
    160
    161    @Override
    162    public Collection<V> values() {
    163        final Collection<V> coll = map.values();
    164        return UnmodifiableCollection.unmodifiableCollection(coll);
    165    }
    166
    167    @Override
    168    public boolean isFull() {
    169        return true;
    170    }
    171
    172    @Override
    173    public int maxSize() {
    174        return size();
    175    }
    176
    177}