    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;
    025
    026import org.apache.commons.collections4.MultiSet;
    027import org.apache.commons.collections4.Unmodifiable;
    028import org.apache.commons.collections4.iterators.UnmodifiableIterator;
    029import org.apache.commons.collections4.set.UnmodifiableSet;
    030
    031/**
    032 * Decorates another {@link MultiSet} to ensure it can't be altered.
    033 * <p>
    034 * Attempts to modify it will result in an UnsupportedOperationException.
    035 *
    036 * @param <E> the type held in the multiset
    037 * @since 4.1
    038 */
    039public final class UnmodifiableMultiSet<E>
    040        extends AbstractMultiSetDecorator<E> implements Unmodifiable {
    041
    042    /** Serialization version */
    043    private static final long serialVersionUID = 20150611L;
    044
    045    /**
    046     * Factory method to create an unmodifiable multiset.
    047     * <p>
    048     * If the multiset passed in is already unmodifiable, it is returned.
    049     *
    050     * @param <E>  the type of the elements in the multiset
    051     * @param multiset  the multiset to decorate, may not be null
    052     * @return an unmodifiable MultiSet
    053     * @throws NullPointerException if multiset is null
    054     */
    055    public static <E> MultiSet<E> unmodifiableMultiSet(final MultiSet<? extends E> multiset) {
    056        if (multiset instanceof Unmodifiable) {
    057            @SuppressWarnings("unchecked") // safe to upcast
    058            final MultiSet<E> tmpMultiSet = (MultiSet<E>) multiset;
    059            return tmpMultiSet;
    060        }
    061        return new UnmodifiableMultiSet<>(multiset);
    062    }
    063
    064    //-----------------------------------------------------------------------
    065    /**
    066     * Constructor that wraps (not copies).
    067     *
    068     * @param multiset  the multiset to decorate, may not be null
    069     * @throws NullPointerException if multiset is null
    070     */
    071    @SuppressWarnings("unchecked") // safe to upcast
    072    private UnmodifiableMultiSet(final MultiSet<? extends E> multiset) {
    073        super((MultiSet<E>) multiset);
    074    }
    075
    076    //-----------------------------------------------------------------------
    077    /**
    078     * Write the collection out using a custom routine.
    079     *
    080     * @param out  the output stream
    081     * @throws IOException if an error occurs while writing to the stream
    082     */
    083    private void writeObject(final ObjectOutputStream out) throws IOException {
    084        out.defaultWriteObject();
    085        out.writeObject(decorated());
    086    }
    087
    088    /**
    089     * Read the collection in using a custom routine.
    090     *
    091     * @param in  the input stream
    092     * @throws IOException if an error occurs while reading from the stream
    093     * @throws ClassNotFoundException if an object read from the stream can not be loaded
    094     * @throws ClassCastException if deserialised object has wrong type
    095     */
    096    @SuppressWarnings("unchecked") // will throw CCE, see Javadoc
    097    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
    098        in.defaultReadObject();
    099        setCollection((Collection<E>) in.readObject());
    100    }
    101
    102    //-----------------------------------------------------------------------
    103    @Override
    104    public Iterator<E> iterator() {
    105        return UnmodifiableIterator.<E> unmodifiableIterator(decorated().iterator());
    106    }
    107
    108    @Override
    109    public boolean add(final E object) {
    110        throw new UnsupportedOperationException();
    111    }
    112
    113    @Override
    114    public boolean addAll(final Collection<? extends E> coll) {
    115        throw new UnsupportedOperationException();
    116    }
    117
    118    @Override
    119    public void clear() {
    120        throw new UnsupportedOperationException();
    121    }
    122
    123    @Override
    124    public boolean remove(final Object object) {
    125        throw new UnsupportedOperationException();
    126    }
    127
    128    @Override
    129    public boolean removeAll(final Collection<?> coll) {
    130        throw new UnsupportedOperationException();
    131    }
    132
    133    @Override
    134    public boolean retainAll(final Collection<?> coll) {
    135        throw new UnsupportedOperationException();
    136    }
    137
    138    //-----------------------------------------------------------------------
    139    @Override
    140    public int setCount(final E object, final int count) {
    141        throw new UnsupportedOperationException();
    142    }
    143
    144    @Override
    145    public int add(final E object, final int count) {
    146        throw new UnsupportedOperationException();
    147    }
    148
    149    @Override
    150    public int remove(final Object object, final int count) {
    151        throw new UnsupportedOperationException();
    152    }
    153
    154    @Override
    155    public Set<E> uniqueSet() {
    156        final Set<E> set = decorated().uniqueSet();
    157        return UnmodifiableSet.unmodifiableSet(set);
    158    }
    159
    160    @Override
    161    public Set<MultiSet.Entry<E>> entrySet() {
    162        final Set<MultiSet.Entry<E>> set = decorated().entrySet();
    163        return UnmodifiableSet.unmodifiableSet(set);
    164    }
    165
    166}