    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.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     *
    052     * @param <E>  the type of the elements in the multiset
    053     * @param multiset  the multiset to decorate, may not be null
    054     * @return an unmodifiable MultiSet
    055     * @throws NullPointerException if multiset is null
    056     */
    057    public static <E> MultiSet<E> unmodifiableMultiSet(final MultiSet<? extends E> multiset) {
    058        if (multiset instanceof Unmodifiable) {
    059            @SuppressWarnings("unchecked") // safe to upcast
    060            final MultiSet<E> tmpMultiSet = (MultiSet<E>) multiset;
    061            return tmpMultiSet;
    062        }
    063        return new UnmodifiableMultiSet<>(multiset);
    064    }
    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    /**
    080     * Write the collection out using a custom routine.
    081     *
    082     * @param out  the output stream
    083     * @throws IOException if an error occurs while writing to the stream
    084     */
    085    private void writeObject(final ObjectOutputStream out) throws IOException {
    086        out.defaultWriteObject();
    087        out.writeObject(decorated());
    088    }
    089
    090    /**
    091     * Read the collection in using a custom routine.
    092     *
    093     * @param in  the input stream
    094     * @throws IOException if an error occurs while reading from the stream
    095     * @throws ClassNotFoundException if an object read from the stream can not be loaded
    096     * @throws ClassCastException if deserialised object has wrong type
    097     */
    098    @SuppressWarnings("unchecked") // will throw CCE, see Javadoc
    099    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
    100        in.defaultReadObject();
    101        setCollection((Collection<E>) in.readObject());
    102    }
    103
    104    //-----------------------------------------------------------------------
    105    @Override
    106    public Iterator<E> iterator() {
    107        return UnmodifiableIterator.<E> unmodifiableIterator(decorated().iterator());
    108    }
    109
    110    @Override
    111    public boolean add(final E object) {
    112        throw new UnsupportedOperationException();
    113    }
    114
    115    @Override
    116    public boolean addAll(final Collection<? extends E> coll) {
    117        throw new UnsupportedOperationException();
    118    }
    119
    120    @Override
    121    public void clear() {
    122        throw new UnsupportedOperationException();
    123    }
    124
    125    @Override
    126    public boolean remove(final Object object) {
    127        throw new UnsupportedOperationException();
    128    }
    129
    130    /**
    131     * @since 4.4
    132     */
    133    @Override
    134    public boolean removeIf(Predicate<? super E> filter) {
    135        throw new UnsupportedOperationException();
    136    }
    137
    138    @Override
    139    public boolean removeAll(final Collection<?> coll) {
    140        throw new UnsupportedOperationException();
    141    }
    142
    143    @Override
    144    public boolean retainAll(final Collection<?> coll) {
    145        throw new UnsupportedOperationException();
    146    }
    147
    148    //-----------------------------------------------------------------------
    149    @Override
    150    public int setCount(final E object, final int count) {
    151        throw new UnsupportedOperationException();
    152    }
    153
    154    @Override
    155    public int add(final E object, final int count) {
    156        throw new UnsupportedOperationException();
    157    }
    158
    159    @Override
    160    public int remove(final Object object, final int count) {
    161        throw new UnsupportedOperationException();
    162    }
    163
    164    @Override
    165    public Set<E> uniqueSet() {
    166        final Set<E> set = decorated().uniqueSet();
    167        return UnmodifiableSet.unmodifiableSet(set);
    168    }
    169
    170    @Override
    171    public Set<MultiSet.Entry<E>> entrySet() {
    172        final Set<MultiSet.Entry<E>> set = decorated().entrySet();
    173        return UnmodifiableSet.unmodifiableSet(set);
    174    }
    175
    176}