    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    /**
    072     * Constructor that wraps (not copies).
    073     *
    074     * @param bag  the bag to decorate, must not be null
    075     * @throws NullPointerException if bag is null
    076     */
    077    @SuppressWarnings("unchecked") // safe to upcast
    078    private UnmodifiableBag(final Bag<? extends E> bag) {
    079        super((Bag<E>) bag);
    080    }
    081
    082    //-----------------------------------------------------------------------
    083    /**
    084     * Write the collection out using a custom routine.
    085     *
    086     * @param out  the output stream
    087     * @throws IOException if an error occurs while writing to the stream
    088     */
    089    private void writeObject(final ObjectOutputStream out) throws IOException {
    090        out.defaultWriteObject();
    091        out.writeObject(decorated());
    092    }
    093
    094    /**
    095     * Read the collection in using a custom routine.
    096     *
    097     * @param in  the input stream
    098     * @throws IOException if an error occurs while reading from the stream
    099     * @throws ClassNotFoundException if an object read from the stream can not be loaded
    100     * @throws ClassCastException if deserialised object has wrong type
    101     */
    102    @SuppressWarnings("unchecked") // will throw CCE, see Javadoc
    103    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
    104        in.defaultReadObject();
    105        setCollection((Collection<E>) in.readObject());
    106    }
    107
    108    //-----------------------------------------------------------------------
    109    @Override
    110    public Iterator<E> iterator() {
    111        return UnmodifiableIterator.<E> unmodifiableIterator(decorated().iterator());
    112    }
    113
    114    @Override
    115    public boolean add(final E object) {
    116        throw new UnsupportedOperationException();
    117    }
    118
    119    @Override
    120    public boolean addAll(final Collection<? extends E> coll) {
    121        throw new UnsupportedOperationException();
    122    }
    123
    124    @Override
    125    public void clear() {
    126        throw new UnsupportedOperationException();
    127    }
    128
    129    @Override
    130    public boolean remove(final Object object) {
    131        throw new UnsupportedOperationException();
    132    }
    133
    134    /**
    135     * @since 4.4
    136     */
    137    @Override
    138    public boolean removeIf(Predicate<? super E> filter) {
    139        throw new UnsupportedOperationException();
    140    }
    141
    142    @Override
    143    public boolean removeAll(final Collection<?> coll) {
    144        throw new UnsupportedOperationException();
    145    }
    146
    147    @Override
    148    public boolean retainAll(final Collection<?> coll) {
    149        throw new UnsupportedOperationException();
    150    }
    151
    152    //-----------------------------------------------------------------------
    153    @Override
    154    public boolean add(final E object, final int count) {
    155        throw new UnsupportedOperationException();
    156    }
    157
    158    @Override
    159    public boolean remove(final Object object, final int count) {
    160        throw new UnsupportedOperationException();
    161    }
    162
    163    @Override
    164    public Set<E> uniqueSet() {
    165        final Set<E> set = decorated().uniqueSet();
    166        return UnmodifiableSet.<E> unmodifiableSet(set);
    167    }
    168
    169}