    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.multiset;
    018
    019import java.io.IOException;
    020import java.io.ObjectInputStream;
    021import java.io.ObjectOutputStream;
    022import java.util.Collection;
    023import java.util.Iterator;
    024import java.util.Set;
    025import java.util.function.Predicate;
    026
    027import org.apache.commons.collections4.MultiSet;
    028import org.apache.commons.collections4.Unmodifiable;
    029import org.apache.commons.collections4.iterators.UnmodifiableIterator;
    030import org.apache.commons.collections4.set.UnmodifiableSet;
    031
    032/**
    033 * Decorates another {@link MultiSet} to ensure it can't be altered.
    034 * <p>
    035 * Attempts to modify it will result in an UnsupportedOperationException.
    036 * </p>
    037 *
    038 * @param <E> The type held in the multiset
    039 * @since 4.1
    040 */
    041public final class UnmodifiableMultiSet<E>
    042        extends AbstractMultiSetDecorator<E> implements Unmodifiable {
    043
    044    /** Serialization version */
    045    private static final long serialVersionUID = 20150611L;
    046
    047    /**
    048     * Factory method to create an unmodifiable multiset.
    049     * <p>
    050     * If the multiset passed in is already unmodifiable, it is returned.
    051     * </p>
    052     *
    053     * @param <E>  the type of the elements in the multiset
    054     * @param multiset  The multiset to decorate, may not be null
    055     * @return An unmodifiable MultiSet
    056     * @throws NullPointerException if multiset is null
    057     */
    058    public static <E> MultiSet<E> unmodifiableMultiSet(final MultiSet<? extends E> multiset) {
    059        if (multiset instanceof Unmodifiable) {
    060            @SuppressWarnings("unchecked") // safe to upcast
    061            final MultiSet<E> tmpMultiSet = (MultiSet<E>) multiset;
    062            return tmpMultiSet;
    063        }
    064        return new UnmodifiableMultiSet<>(multiset);
    065    }
    066
    067    /**
    068     * Constructor that wraps (not copies).
    069     *
    070     * @param multiset  The multiset to decorate, may not be null
    071     * @throws NullPointerException if multiset is null
    072     */
    073    @SuppressWarnings("unchecked") // safe to upcast
    074    private UnmodifiableMultiSet(final MultiSet<? extends E> multiset) {
    075        super((MultiSet<E>) multiset);
    076    }
    077
    078    /**
    079     * Always throws {@link UnsupportedOperationException}.
    080     *
    081     * @param object Ignored.
    082     * @throws UnsupportedOperationException Always thrown.
    083     */
    084    @Override
    085    public boolean add(final E object) {
    086        throw new UnsupportedOperationException();
    087    }
    088
    089    /**
    090     * Always throws {@link UnsupportedOperationException}.
    091     *
    092     * @param object Ignored.
    093     * @param count Ignored.
    094     * @throws UnsupportedOperationException Always thrown.
    095     */
    096    @Override
    097    public int add(final E object, final int count) {
    098        throw new UnsupportedOperationException();
    099    }
    100
    101    /**
    102     * Always throws {@link UnsupportedOperationException}.
    103     *
    104     * @param coll Ignored.
    105     * @throws UnsupportedOperationException Always thrown.
    106     */
    107    @Override
    108    public boolean addAll(final Collection<? extends E> coll) {
    109        throw new UnsupportedOperationException();
    110    }
    111
    112    /**
    113     * Always throws {@link UnsupportedOperationException}.
    114     *
    115     * @throws UnsupportedOperationException Always thrown.
    116     */
    117    @Override
    118    public void clear() {
    119        throw new UnsupportedOperationException();
    120    }
    121
    122    @Override
    123    public Set<MultiSet.Entry<E>> entrySet() {
    124        return UnmodifiableSet.unmodifiableSet(decorated().entrySet());
    125    }
    126
    127    @Override
    128    public Iterator<E> iterator() {
    129        return UnmodifiableIterator.<E>unmodifiableIterator(decorated().iterator());
    130    }
    131
    132    /**
    133     * Deserializes the collection in using a custom routine.
    134     *
    135     * @param in  The input stream
    136     * @throws IOException Thrown if an error occurs while reading from the stream
    137     * @throws ClassNotFoundException if an object read from the stream cannot be loaded
    138     * @throws ClassCastException if deserialized object has wrong type
    139     */
    140    @SuppressWarnings("unchecked") // will throw CCE, see Javadoc
    141    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
    142        in.defaultReadObject();
    143        setCollection((Collection<E>) in.readObject());
    144    }
    145
    146    /**
    147     * Always throws {@link UnsupportedOperationException}.
    148     *
    149     * @param object Ignored.
    150     * @throws UnsupportedOperationException Always thrown.
    151     */
    152    @Override
    153    public boolean remove(final Object object) {
    154        throw new UnsupportedOperationException();
    155    }
    156
    157    /**
    158     * Always throws {@link UnsupportedOperationException}.
    159     *
    160     * @param object Ignored.
    161     * @param count Ignored.
    162     * @throws UnsupportedOperationException Always thrown.
    163     */
    164    @Override
    165    public int remove(final Object object, final int count) {
    166        throw new UnsupportedOperationException();
    167    }
    168
    169    /**
    170     * Always throws {@link UnsupportedOperationException}.
    171     *
    172     * @param coll Ignored.
    173     * @throws UnsupportedOperationException Always thrown.
    174     */
    175    @Override
    176    public boolean removeAll(final Collection<?> coll) {
    177        throw new UnsupportedOperationException();
    178    }
    179
    180    /**
    181     * Always throws {@link UnsupportedOperationException}.
    182     *
    183     * @param filter Ignored.
    184     * @throws UnsupportedOperationException Always thrown.
    185     * @since 4.4
    186     */
    187    @Override
    188    public boolean removeIf(final Predicate<? super E> filter) {
    189        throw new UnsupportedOperationException();
    190    }
    191
    192    /**
    193     * Always throws {@link UnsupportedOperationException}.
    194     *
    195     * @param coll Ignored.
    196     * @throws UnsupportedOperationException Always thrown.
    197     */
    198    @Override
    199    public boolean retainAll(final Collection<?> coll) {
    200        throw new UnsupportedOperationException();
    201    }
    202
    203    /**
    204     * Always throws {@link UnsupportedOperationException}.
    205     *
    206     * @param object Ignored.
    207     * @param count Ignored.
    208     * @throws UnsupportedOperationException Always thrown.
    209     */
    210    @Override
    211    public int setCount(final E object, final int count) {
    212        throw new UnsupportedOperationException();
    213    }
    214
    215    @Override
    216    public Set<E> uniqueSet() {
    217        return UnmodifiableSet.unmodifiableSet(decorated().uniqueSet());
    218    }
    219
    220    /**
    221     * Serializes this object to an ObjectOutputStream.
    222     *
    223     * @param out The target ObjectOutputStream.
    224     * @throws IOException thrown when an I/O errors occur writing to the target stream.
    225     */
    226    private void writeObject(final ObjectOutputStream out) throws IOException {
    227        out.defaultWriteObject();
    228        out.writeObject(decorated());
    229    }
    230
    231}