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