    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     * Constructor that wraps (not copies).
    068     *
    069     * @param multiset  the multiset to decorate, may not be null
    070     * @throws NullPointerException if multiset is null
    071     */
    072    @SuppressWarnings("unchecked") // safe to upcast
    073    private UnmodifiableMultiSet(final MultiSet<? extends E> multiset) {
    074        super((MultiSet<E>) multiset);
    075    }
    076
    077    @Override
    078    public boolean add(final E object) {
    079        throw new UnsupportedOperationException();
    080    }
    081
    082    @Override
    083    public int add(final E object, final int count) {
    084        throw new UnsupportedOperationException();
    085    }
    086
    087    @Override
    088    public boolean addAll(final Collection<? extends E> coll) {
    089        throw new UnsupportedOperationException();
    090    }
    091
    092    @Override
    093    public void clear() {
    094        throw new UnsupportedOperationException();
    095    }
    096
    097    @Override
    098    public Set<MultiSet.Entry<E>> entrySet() {
    099        final Set<MultiSet.Entry<E>> set = decorated().entrySet();
    100        return UnmodifiableSet.unmodifiableSet(set);
    101    }
    102
    103    @Override
    104    public Iterator<E> iterator() {
    105        return UnmodifiableIterator.<E>unmodifiableIterator(decorated().iterator());
    106    }
    107
    108    /**
    109     * Read the collection in using a custom routine.
    110     *
    111     * @param in  the input stream
    112     * @throws IOException if an error occurs while reading from the stream
    113     * @throws ClassNotFoundException if an object read from the stream can not be loaded
    114     * @throws ClassCastException if deserialized object has wrong type
    115     */
    116    @SuppressWarnings("unchecked") // will throw CCE, see Javadoc
    117    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
    118        in.defaultReadObject();
    119        setCollection((Collection<E>) in.readObject());
    120    }
    121
    122    @Override
    123    public boolean remove(final Object object) {
    124        throw new UnsupportedOperationException();
    125    }
    126
    127    @Override
    128    public int remove(final Object object, final int count) {
    129        throw new UnsupportedOperationException();
    130    }
    131
    132    @Override
    133    public boolean removeAll(final Collection<?> coll) {
    134        throw new UnsupportedOperationException();
    135    }
    136
    137    /**
    138     * @since 4.4
    139     */
    140    @Override
    141    public boolean removeIf(final Predicate<? super E> filter) {
    142        throw new UnsupportedOperationException();
    143    }
    144
    145    @Override
    146    public boolean retainAll(final Collection<?> coll) {
    147        throw new UnsupportedOperationException();
    148    }
    149
    150    @Override
    151    public int setCount(final E object, final int count) {
    152        throw new UnsupportedOperationException();
    153    }
    154
    155    @Override
    156    public Set<E> uniqueSet() {
    157        final Set<E> set = decorated().uniqueSet();
    158        return UnmodifiableSet.unmodifiableSet(set);
    159    }
    160
    161    /**
    162     * Write the collection out using a custom routine.
    163     *
    164     * @param out  the output stream
    165     * @throws IOException if an error occurs while writing to the stream
    166     */
    167    private void writeObject(final ObjectOutputStream out) throws IOException {
    168        out.defaultWriteObject();
    169        out.writeObject(decorated());
    170    }
    171
    172}