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}