    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.bag;
    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.Bag;
    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 Bag} to ensure it can't be altered.
    034 * <p>
    035 * This class is Serializable from Commons Collections 3.1.
    036 * </p>
    037 * <p>
    038 * Attempts to modify it will result in an UnsupportedOperationException.
    039 * </p>
    040 *
    041 * @param <E> the type of elements in this bag
    042 * @since 3.0
    043 */
    044public final class UnmodifiableBag<E>
    045        extends AbstractBagDecorator<E> implements Unmodifiable {
    046
    047    /** Serialization version */
    048    private static final long serialVersionUID = -1873799975157099624L;
    049
    050    /**
    051     * Factory method to create an unmodifiable bag.
    052     * <p>
    053     * If the bag passed in is already unmodifiable, it is returned.
    054     *
    055     * @param <E> the type of the elements in the bag
    056     * @param bag  the bag to decorate, must not be null
    057     * @return an unmodifiable Bag
    058     * @throws NullPointerException if bag is null
    059     * @since 4.0
    060     */
    061    public static <E> Bag<E> unmodifiableBag(final Bag<? extends E> bag) {
    062        if (bag instanceof Unmodifiable) {
    063            @SuppressWarnings("unchecked") // safe to upcast
    064            final Bag<E> tmpBag = (Bag<E>) bag;
    065            return tmpBag;
    066        }
    067        return new UnmodifiableBag<>(bag);
    068    }
    069
    070    /**
    071     * Constructor that wraps (not copies).
    072     *
    073     * @param bag  the bag to decorate, must not be null
    074     * @throws NullPointerException if bag is null
    075     */
    076    @SuppressWarnings("unchecked") // safe to upcast
    077    private UnmodifiableBag(final Bag<? extends E> bag) {
    078        super((Bag<E>) bag);
    079    }
    080
    081    @Override
    082    public boolean add(final E object) {
    083        throw new UnsupportedOperationException();
    084    }
    085
    086    @Override
    087    public boolean add(final E object, final int count) {
    088        throw new UnsupportedOperationException();
    089    }
    090
    091    @Override
    092    public boolean addAll(final Collection<? extends E> coll) {
    093        throw new UnsupportedOperationException();
    094    }
    095
    096    @Override
    097    public void clear() {
    098        throw new UnsupportedOperationException();
    099    }
    100
    101    @Override
    102    public Iterator<E> iterator() {
    103        return UnmodifiableIterator.<E>unmodifiableIterator(decorated().iterator());
    104    }
    105
    106    /**
    107     * Read the collection in using a custom routine.
    108     *
    109     * @param in  the input stream
    110     * @throws IOException if an error occurs while reading from the stream
    111     * @throws ClassNotFoundException if an object read from the stream can not be loaded
    112     * @throws ClassCastException if deserialized object has wrong type
    113     */
    114    @SuppressWarnings("unchecked") // will throw CCE, see Javadoc
    115    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
    116        in.defaultReadObject();
    117        setCollection((Collection<E>) in.readObject());
    118    }
    119
    120    @Override
    121    public boolean remove(final Object object) {
    122        throw new UnsupportedOperationException();
    123    }
    124
    125    @Override
    126    public boolean remove(final Object object, final int count) {
    127        throw new UnsupportedOperationException();
    128    }
    129
    130    @Override
    131    public boolean removeAll(final Collection<?> coll) {
    132        throw new UnsupportedOperationException();
    133    }
    134
    135    /**
    136     * @since 4.4
    137     */
    138    @Override
    139    public boolean removeIf(final Predicate<? super E> filter) {
    140        throw new UnsupportedOperationException();
    141    }
    142
    143    @Override
    144    public boolean retainAll(final Collection<?> coll) {
    145        throw new UnsupportedOperationException();
    146    }
    147
    148    @Override
    149    public Set<E> uniqueSet() {
    150        final Set<E> set = decorated().uniqueSet();
    151        return UnmodifiableSet.<E>unmodifiableSet(set);
    152    }
    153
    154    /**
    155     * Write the collection out using a custom routine.
    156     *
    157     * @param out  the output stream
    158     * @throws IOException if an error occurs while writing to the stream
    159     */
    160    private void writeObject(final ObjectOutputStream out) throws IOException {
    161        out.defaultWriteObject();
    162        out.writeObject(decorated());
    163    }
    164
    165}