    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.collection;
    018
    019import java.util.ArrayList;
    020import java.util.Collection;
    021import java.util.Collections;
    022import java.util.HashSet;
    023import java.util.LinkedList;
    024import java.util.List;
    025import java.util.Queue;
    026import java.util.Set;
    027
    028import org.apache.commons.collections4.Bag;
    029import org.apache.commons.collections4.MultiSet;
    030import org.apache.commons.collections4.Predicate;
    031import org.apache.commons.collections4.bag.HashBag;
    032import org.apache.commons.collections4.bag.PredicatedBag;
    033import org.apache.commons.collections4.functors.NotNullPredicate;
    034import org.apache.commons.collections4.list.PredicatedList;
    035import org.apache.commons.collections4.multiset.HashMultiSet;
    036import org.apache.commons.collections4.multiset.PredicatedMultiSet;
    037import org.apache.commons.collections4.queue.PredicatedQueue;
    038import org.apache.commons.collections4.set.PredicatedSet;
    039
    040/**
    041 * Decorates another {@link Collection} to validate that additions
    042 * match a specified predicate.
    043 * <p>
    044 * This collection exists to provide validation for the decorated collection.
    045 * It is normally created to decorate an empty collection.
    046 * If an object cannot be added to the collection, an IllegalArgumentException is thrown.
    047 * </p>
    048 * <p>
    049 * One usage would be to ensure that no null entries are added to the collection:
    050 * </p>
    051 * <pre>
    052 * Collection coll = PredicatedCollection.predicatedCollection(new ArrayList(), NotNullPredicate.INSTANCE);
    053 * </pre>
    054 * <p>
    055 * This class is Serializable from Commons Collections 3.1.
    056 * </p>
    057 *
    058 * @param <E> the type of the elements in the collection
    059 * @since 3.0
    060 */
    061public class PredicatedCollection<E> extends AbstractCollectionDecorator<E> {
    062
    063    /** Serialization version */
    064    private static final long serialVersionUID = -5259182142076705162L;
    065
    066    /** The predicate to use */
    067    protected final Predicate<? super E> predicate;
    068
    069    /**
    070     * Returns a Builder with the given predicate.
    071     *
    072     * @param <E>  the element type
    073     * @param predicate  the predicate to use
    074     * @return a new Builder for predicated collections
    075     * @since 4.1
    076     */
    077    public static <E> Builder<E> builder(final Predicate<? super E> predicate) {
    078        return new Builder<>(predicate);
    079    }
    080
    081    /**
    082     * Returns a Builder with a NotNullPredicate.
    083     *
    084     * @param <E>  the element type
    085     * @return a new Builder for predicated collections that ignores null values.
    086     * @since 4.1
    087     */
    088    public static <E> Builder<E> notNullBuilder() {
    089        return new Builder<>(NotNullPredicate.<E>notNullPredicate());
    090    }
    091
    092    /**
    093     * Factory method to create a predicated (validating) collection.
    094     * <p>
    095     * If there are any elements already in the collection being decorated, they
    096     * are validated.
    097     *
    098     * @param <T> the type of the elements in the collection
    099     * @param coll  the collection to decorate, must not be null
    100     * @param predicate  the predicate to use for validation, must not be null
    101     * @return a new predicated collection
    102     * @throws NullPointerException if collection or predicate is null
    103     * @throws IllegalArgumentException if the collection contains invalid elements
    104     * @since 4.0
    105     */
    106    public static <T> PredicatedCollection<T> predicatedCollection(final Collection<T> coll,
    107                                                                   final Predicate<? super T> predicate) {
    108        return new PredicatedCollection<>(coll, predicate);
    109    }
    110
    111    //-----------------------------------------------------------------------
    112    /**
    113     * Constructor that wraps (not copies).
    114     * <p>
    115     * If there are any elements already in the collection being decorated, they
    116     * are validated.
    117     *
    118     * @param coll  the collection to decorate, must not be null
    119     * @param predicate  the predicate to use for validation, must not be null
    120     * @throws NullPointerException if collection or predicate is null
    121     * @throws IllegalArgumentException if the collection contains invalid elements
    122     */
    123    protected PredicatedCollection(final Collection<E> coll, final Predicate<? super E> predicate) {
    124        super(coll);
    125        if (predicate == null) {
    126            throw new NullPointerException("Predicate must not be null.");
    127        }
    128        this.predicate = predicate;
    129        for (final E item : coll) {
    130            validate(item);
    131        }
    132    }
    133
    134    /**
    135     * Validates the object being added to ensure it matches the predicate.
    136     * <p>
    137     * The predicate itself should not throw an exception, but return false to
    138     * indicate that the object cannot be added.
    139     *
    140     * @param object  the object being added
    141     * @throws IllegalArgumentException if the add is invalid
    142     */
    143    protected void validate(final E object) {
    144        if (predicate.evaluate(object) == false) {
    145            throw new IllegalArgumentException("Cannot add Object '" + object + "' - Predicate '" +
    146                                               predicate + "' rejected it");
    147        }
    148    }
    149
    150    //-----------------------------------------------------------------------
    151    /**
    152     * Override to validate the object being added to ensure it matches
    153     * the predicate.
    154     *
    155     * @param object  the object being added
    156     * @return the result of adding to the underlying collection
    157     * @throws IllegalArgumentException if the add is invalid
    158     */
    159    @Override
    160    public boolean add(final E object) {
    161        validate(object);
    162        return decorated().add(object);
    163    }
    164
    165    /**
    166     * Override to validate the objects being added to ensure they match
    167     * the predicate. If any one fails, no update is made to the underlying
    168     * collection.
    169     *
    170     * @param coll  the collection being added
    171     * @return the result of adding to the underlying collection
    172     * @throws IllegalArgumentException if the add is invalid
    173     */
    174    @Override
    175    public boolean addAll(final Collection<? extends E> coll) {
    176        for (final E item : coll) {
    177            validate(item);
    178        }
    179        return decorated().addAll(coll);
    180    }
    181
    182    /**
    183     * Builder for creating predicated collections.
    184     * <p>
    185     * Create a Builder with a predicate to validate elements against, then add any elements
    186     * to the builder. Elements that fail the predicate will be added to a rejected list.
    187     * Finally create or decorate a collection using the createPredicated[List,Set,Bag,Queue] methods.
    188     * <p>
    189     * An example:
    190     * <pre>
    191     *   Predicate&lt;String&gt; predicate = NotNullPredicate.notNullPredicate();
    192     *   PredicatedCollectionBuilder&lt;String&gt; builder = PredicatedCollection.builder(predicate);
    193     *   builder.add("item1");
    194     *   builder.add(null);
    195     *   builder.add("item2");
    196     *   List&lt;String&gt; predicatedList = builder.createPredicatedList();
    197     * </pre>
    198     * <p>
    199     * At the end of the code fragment above predicatedList is protected by the predicate supplied
    200     * to the builder and it contains item1 and item2.
    201     * <p>
    202     * More elements can be added to the builder once a predicated collection has been created,
    203     * but these elements will not be reflected in already created collections.
    204     *
    205     * @param <E>  the element type
    206     * @since 4.1
    207     */
    208    public static class Builder<E> {
    209
    210        /** The predicate to use. */
    211        private final Predicate<? super E> predicate;
    212
    213        /** The buffer containing valid elements. */
    214        private final List<E> accepted = new ArrayList<>();
    215
    216        /** The buffer containing rejected elements. */
    217        private final List<E> rejected = new ArrayList<>();
    218
    219        // -----------------------------------------------------------------------
    220        /**
    221         * Constructs a PredicatedCollectionBuilder with the specified Predicate.
    222         *
    223         * @param predicate  the predicate to use
    224         * @throws NullPointerException if predicate is null
    225         */
    226        public Builder(final Predicate<? super E> predicate) {
    227            if (predicate == null) {
    228                throw new NullPointerException("Predicate must not be null");
    229            }
    230            this.predicate = predicate;
    231        }
    232
    233        /**
    234         * Adds the item to the builder.
    235         * <p>
    236         * If the predicate is true, it is added to the list of accepted elements,
    237         * otherwise it is added to the rejected list.
    238         *
    239         * @param item  the element to add
    240         * @return the PredicatedCollectionBuilder.
    241         */
    242        public Builder<E> add(final E item) {
    243            if (predicate.evaluate(item)) {
    244                accepted.add(item);
    245            } else {
    246                rejected.add(item);
    247            }
    248            return this;
    249        }
    250
    251        /**
    252         * Adds all elements from the given collection to the builder.
    253         * <p>
    254         * All elements for which the predicate evaluates to true will be added to the
    255         * list of accepted elements, otherwise they are added to the rejected list.
    256         *
    257         * @param items  the elements to add to the builder
    258         * @return the PredicatedCollectionBuilder.
    259         */
    260        public Builder<E> addAll(final Collection<? extends E> items) {
    261            if (items != null) {
    262                for (final E item : items) {
    263                    add(item);
    264                }
    265            }
    266            return this;
    267        }
    268
    269        /**
    270         * Create a new predicated list filled with the accepted elements.
    271         * <p>
    272         * The builder is not modified by this method, so it is possible to create more collections
    273         * or add more elements afterwards. Further changes will not propagate to the returned list.
    274         *
    275         * @return a new predicated list.
    276         */
    277        public List<E> createPredicatedList() {
    278            return createPredicatedList(new ArrayList<E>());
    279        }
    280
    281        /**
    282         * Decorates the given list with validating behavior using the predicate. All accepted elements
    283         * are appended to the list. If the list already contains elements, they are validated.
    284         * <p>
    285         * The builder is not modified by this method, so it is possible to create more collections
    286         * or add more elements afterwards. Further changes will not propagate to the returned list.
    287         *
    288         * @param list  the List to decorate, must not be null
    289         * @return the decorated list.
    290         * @throws NullPointerException if list is null
    291         * @throws IllegalArgumentException if list contains invalid elements
    292         */
    293        public List<E> createPredicatedList(final List<E> list) {
    294            if (list == null) {
    295                throw new NullPointerException("List must not be null.");
    296            }
    297            final List<E> predicatedList = PredicatedList.predicatedList(list, predicate);
    298            predicatedList.addAll(accepted);
    299            return predicatedList;
    300        }
    301
    302        /**
    303         * Create a new predicated set filled with the accepted elements.
    304         * <p>
    305         * The builder is not modified by this method, so it is possible to create more collections
    306         * or add more elements afterwards. Further changes will not propagate to the returned set.
    307         *
    308         * @return a new predicated set.
    309         */
    310        public Set<E> createPredicatedSet() {
    311            return createPredicatedSet(new HashSet<E>());
    312        }
    313
    314        /**
    315         * Decorates the given list with validating behavior using the predicate. All accepted elements
    316         * are appended to the set. If the set already contains elements, they are validated.
    317         * <p>
    318         * The builder is not modified by this method, so it is possible to create more collections
    319         * or add more elements afterwards. Further changes will not propagate to the returned set.
    320         *
    321         * @param set  the set to decorate, must not be null
    322         * @return the decorated set.
    323         * @throws NullPointerException if set is null
    324         * @throws IllegalArgumentException if set contains invalid elements
    325         */
    326        public Set<E> createPredicatedSet(final Set<E> set) {
    327            if (set == null) {
    328                throw new NullPointerException("Set must not be null.");
    329            }
    330            final PredicatedSet<E> predicatedSet = PredicatedSet.predicatedSet(set, predicate);
    331            predicatedSet.addAll(accepted);
    332            return predicatedSet;
    333        }
    334
    335        /**
    336         * Create a new predicated multiset filled with the accepted elements.
    337         * <p>
    338         * The builder is not modified by this method, so it is possible to create more collections
    339         * or add more elements afterwards. Further changes will not propagate to the returned multiset.
    340         *
    341         * @return a new predicated multiset.
    342         */
    343        public MultiSet<E> createPredicatedMultiSet() {
    344            return createPredicatedMultiSet(new HashMultiSet<E>());
    345        }
    346
    347        /**
    348         * Decorates the given multiset with validating behavior using the predicate. All accepted elements
    349         * are appended to the multiset. If the multiset already contains elements, they are validated.
    350         * <p>
    351         * The builder is not modified by this method, so it is possible to create more collections
    352         * or add more elements afterwards. Further changes will not propagate to the returned multiset.
    353         *
    354         * @param multiset  the multiset to decorate, must not be null
    355         * @return the decorated multiset.
    356         * @throws NullPointerException if multiset is null
    357         * @throws IllegalArgumentException if multiset contains invalid elements
    358         */
    359        public MultiSet<E> createPredicatedMultiSet(final MultiSet<E> multiset) {
    360            if (multiset == null) {
    361                throw new NullPointerException("MultiSet must not be null.");
    362            }
    363            final PredicatedMultiSet<E> predicatedMultiSet =
    364                    PredicatedMultiSet.predicatedMultiSet(multiset, predicate);
    365            predicatedMultiSet.addAll(accepted);
    366            return predicatedMultiSet;
    367        }
    368
    369        /**
    370         * Create a new predicated bag filled with the accepted elements.
    371         * <p>
    372         * The builder is not modified by this method, so it is possible to create more collections
    373         * or add more elements afterwards. Further changes will not propagate to the returned bag.
    374         *
    375         * @return a new predicated bag.
    376         */
    377        public Bag<E> createPredicatedBag() {
    378            return createPredicatedBag(new HashBag<E>());
    379        }
    380
    381        /**
    382         * Decorates the given bag with validating behavior using the predicate. All accepted elements
    383         * are appended to the bag. If the bag already contains elements, they are validated.
    384         * <p>
    385         * The builder is not modified by this method, so it is possible to create more collections
    386         * or add more elements afterwards. Further changes will not propagate to the returned bag.
    387         *
    388         * @param bag  the bag to decorate, must not be null
    389         * @return the decorated bag.
    390         * @throws NullPointerException if bag is null
    391         * @throws IllegalArgumentException if bag contains invalid elements
    392         */
    393        public Bag<E> createPredicatedBag(final Bag<E> bag) {
    394            if (bag == null) {
    395                throw new NullPointerException("Bag must not be null.");
    396            }
    397            final PredicatedBag<E> predicatedBag = PredicatedBag.predicatedBag(bag, predicate);
    398            predicatedBag.addAll(accepted);
    399            return predicatedBag;
    400        }
    401
    402        /**
    403         * Create a new predicated queue filled with the accepted elements.
    404         * <p>
    405         * The builder is not modified by this method, so it is possible to create more collections
    406         * or add more elements afterwards. Further changes will not propagate to the returned queue.
    407         *
    408         * @return a new predicated queue.
    409         */
    410        public Queue<E> createPredicatedQueue() {
    411            return createPredicatedQueue(new LinkedList<E>());
    412        }
    413
    414        /**
    415         * Decorates the given queue with validating behavior using the predicate. All accepted elements
    416         * are appended to the queue. If the queue already contains elements, they are validated.
    417         * <p>
    418         * The builder is not modified by this method, so it is possible to create more collections
    419         * or add more elements afterwards. Further changes will not propagate to the returned queue.
    420         *
    421         * @param queue  the queue to decorate, must not be null
    422         * @return the decorated queue.
    423         * @throws NullPointerException if queue is null
    424         * @throws IllegalArgumentException if queue contains invalid elements
    425         */
    426        public Queue<E> createPredicatedQueue(final Queue<E> queue) {
    427            if (queue == null) {
    428                throw new NullPointerException("queue must not be null");
    429            }
    430            final PredicatedQueue<E> predicatedQueue = PredicatedQueue.predicatedQueue(queue, predicate);
    431            predicatedQueue.addAll(accepted);
    432            return predicatedQueue;
    433        }
    434
    435        /**
    436         * Returns an unmodifiable collection containing all rejected elements.
    437         *
    438         * @return an unmodifiable collection
    439         */
    440        public Collection<E> rejectedElements() {
    441            return Collections.unmodifiableCollection(rejected);
    442        }
    443
    444    }
    445
    446}