    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;
    025
    026import org.apache.commons.collections4.Bag;
    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 Bag} to ensure it can't be altered.
    033 * <p>
    034 * This class is Serializable from Commons Collections 3.1.
    035 * <p>
    036 * Attempts to modify it will result in an UnsupportedOperationException.
    037 *
    038 * @param <E> the type of elements in this bag
    039 * @since 3.0
    040 */
    041public final class UnmodifiableBag<E>
    042        extends AbstractBagDecorator<E> implements Unmodifiable {
    043
    044    /** Serialization version */
    045    private static final long serialVersionUID = -1873799975157099624L;
    046
    047    /**
    048     * Factory method to create an unmodifiable bag.
    049     * <p>
    050     * If the bag passed in is already unmodifiable, it is returned.
    051     *
    052     * @param <E> the type of the elements in the bag
    053     * @param bag  the bag to decorate, must not be null
    054     * @return an unmodifiable Bag
    055     * @throws NullPointerException if bag is null
    056     * @since 4.0
    057     */
    058    public static <E> Bag<E> unmodifiableBag(final Bag<? extends E> bag) {
    059        if (bag instanceof Unmodifiable) {
    060            @SuppressWarnings("unchecked") // safe to upcast
    061            final Bag<E> tmpBag = (Bag<E>) bag;
    062            return tmpBag;
    063        }
    064        return new UnmodifiableBag<>(bag);
    065    }
    066
    067    //-----------------------------------------------------------------------
    068    /**
    069     * Constructor that wraps (not copies).
    070     *
    071     * @param bag  the bag to decorate, must not be null
    072     * @throws NullPointerException if bag is null
    073     */
    074    @SuppressWarnings("unchecked") // safe to upcast
    075    private UnmodifiableBag(final Bag<? extends E> bag) {
    076        super((Bag<E>) bag);
    077    }
    078
    079    //-----------------------------------------------------------------------
    080    /**
    081     * Write the collection out using a custom routine.
    082     *
    083     * @param out  the output stream
    084     * @throws IOException if an error occurs while writing to the stream
    085     */
    086    private void writeObject(final ObjectOutputStream out) throws IOException {
    087        out.defaultWriteObject();
    088        out.writeObject(decorated());
    089    }
    090
    091    /**
    092     * Read the collection in using a custom routine.
    093     *
    094     * @param in  the input stream
    095     * @throws IOException if an error occurs while reading from the stream
    096     * @throws ClassNotFoundException if an object read from the stream can not be loaded
    097     * @throws ClassCastException if deserialised object has wrong type
    098     */
    099    @SuppressWarnings("unchecked") // will throw CCE, see Javadoc
    100    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
    101        in.defaultReadObject();
    102        setCollection((Collection<E>) in.readObject());
    103    }
    104
    105    //-----------------------------------------------------------------------
    106    @Override
    107    public Iterator<E> iterator() {
    108        return UnmodifiableIterator.<E> unmodifiableIterator(decorated().iterator());
    109    }
    110
    111    @Override
    112    public boolean add(final E object) {
    113        throw new UnsupportedOperationException();
    114    }
    115
    116    @Override
    117    public boolean addAll(final Collection<? extends E> coll) {
    118        throw new UnsupportedOperationException();
    119    }
    120
    121    @Override
    122    public void clear() {
    123        throw new UnsupportedOperationException();
    124    }
    125
    126    @Override
    127    public boolean remove(final Object object) {
    128        throw new UnsupportedOperationException();
    129    }
    130
    131    @Override
    132    public boolean removeAll(final Collection<?> coll) {
    133        throw new UnsupportedOperationException();
    134    }
    135
    136    @Override
    137    public boolean retainAll(final Collection<?> coll) {
    138        throw new UnsupportedOperationException();
    139    }
    140
    141    //-----------------------------------------------------------------------
    142    @Override
    143    public boolean add(final E object, final int count) {
    144        throw new UnsupportedOperationException();
    145    }
    146
    147    @Override
    148    public boolean remove(final Object object, final int count) {
    149        throw new UnsupportedOperationException();
    150    }
    151
    152    @Override
    153    public Set<E> uniqueSet() {
    154        final Set<E> set = decorated().uniqueSet();
    155        return UnmodifiableSet.<E> unmodifiableSet(set);
    156    }
    157
    158}