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}