    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.set;
    018
    019import java.io.IOException;
    020import java.io.ObjectInputStream;
    021import java.io.ObjectOutputStream;
    022import java.util.Collection;
    023import java.util.Iterator;
    024import java.util.SortedSet;
    025
    026import org.apache.commons.collections4.Unmodifiable;
    027import org.apache.commons.collections4.iterators.UnmodifiableIterator;
    028
    029/**
    030 * Decorates another <code>SortedSet</code> to ensure it can't be altered.
    031 * <p>
    032 * This class is Serializable from Commons Collections 3.1.
    033 * <p>
    034 * Attempts to modify it will result in an UnsupportedOperationException.
    035 *
    036 * @param <E> the type of the elements in this set
    037 * @since 3.0
    038 */
    039public final class UnmodifiableSortedSet<E>
    040        extends AbstractSortedSetDecorator<E>
    041        implements Unmodifiable {
    042
    043    /** Serialization version */
    044    private static final long serialVersionUID = -725356885467962424L;
    045
    046    /**
    047     * Factory method to create an unmodifiable set.
    048     *
    049     * @param <E> the element type
    050     * @param set  the set to decorate, must not be null
    051     * @return a new unmodifiable {@link SortedSet}
    052     * @throws NullPointerException if set is null
    053     * @since 4.0
    054     */
    055    public static <E> SortedSet<E> unmodifiableSortedSet(final SortedSet<E> set) {
    056        if (set instanceof Unmodifiable) {
    057            return set;
    058        }
    059        return new UnmodifiableSortedSet<>(set);
    060    }
    061
    062    //-----------------------------------------------------------------------
    063    /**
    064     * Constructor that wraps (not copies).
    065     *
    066     * @param set  the set to decorate, must not be null
    067     * @throws NullPointerException if set is null
    068     */
    069    private UnmodifiableSortedSet(final SortedSet<E> set) {
    070        super(set);
    071    }
    072
    073    //-----------------------------------------------------------------------
    074    @Override
    075    public Iterator<E> iterator() {
    076        return UnmodifiableIterator.unmodifiableIterator(decorated().iterator());
    077    }
    078
    079    @Override
    080    public boolean add(final E object) {
    081        throw new UnsupportedOperationException();
    082    }
    083
    084    @Override
    085    public boolean addAll(final Collection<? extends E> coll) {
    086        throw new UnsupportedOperationException();
    087    }
    088
    089    @Override
    090    public void clear() {
    091        throw new UnsupportedOperationException();
    092    }
    093
    094    @Override
    095    public boolean remove(final Object object) {
    096        throw new UnsupportedOperationException();
    097    }
    098
    099    @Override
    100    public boolean removeAll(final Collection<?> coll) {
    101        throw new UnsupportedOperationException();
    102    }
    103
    104    @Override
    105    public boolean retainAll(final Collection<?> coll) {
    106        throw new UnsupportedOperationException();
    107    }
    108
    109    //-----------------------------------------------------------------------
    110    @Override
    111    public SortedSet<E> subSet(final E fromElement, final E toElement) {
    112        final SortedSet<E> sub = decorated().subSet(fromElement, toElement);
    113        return unmodifiableSortedSet(sub);
    114    }
    115
    116    @Override
    117    public SortedSet<E> headSet(final E toElement) {
    118        final SortedSet<E> head = decorated().headSet(toElement);
    119        return unmodifiableSortedSet(head);
    120    }
    121
    122    @Override
    123    public SortedSet<E> tailSet(final E fromElement) {
    124        final SortedSet<E> tail = decorated().tailSet(fromElement);
    125        return unmodifiableSortedSet(tail);
    126    }
    127
    128    //-----------------------------------------------------------------------
    129    /**
    130     * Write the collection out using a custom routine.
    131     *
    132     * @param out  the output stream
    133     * @throws IOException if an error occurs while writing to the stream
    134     */
    135    private void writeObject(final ObjectOutputStream out) throws IOException {
    136        out.defaultWriteObject();
    137        out.writeObject(decorated());
    138    }
    139
    140    /**
    141     * Read the collection in using a custom routine.
    142     *
    143     * @param in  the input stream
    144     * @throws IOException if an error occurs while reading from the stream
    145     * @throws ClassNotFoundException if an object read from the stream can not be loaded
    146     */
    147    @SuppressWarnings("unchecked") // (1) should only fail if input stream is incorrect
    148    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
    149        in.defaultReadObject();
    150        setCollection((Collection<E>) in.readObject()); // (1)
    151    }
    152
    153}