    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.NavigableSet;
    025import java.util.SortedSet;
    026
    027import org.apache.commons.collections4.Unmodifiable;
    028import org.apache.commons.collections4.iterators.UnmodifiableIterator;
    029
    030/**
    031 * Decorates another <code>NavigableSet</code> to ensure it can't be altered.
    032 * <p>
    033 * Attempts to modify it will result in an UnsupportedOperationException.
    034 *
    035 * @param <E> the type of the elements in this set
    036 * @since 4.1
    037 */
    038public final class UnmodifiableNavigableSet<E>
    039        extends AbstractNavigableSetDecorator<E>
    040        implements Unmodifiable {
    041
    042    /** Serialization version */
    043    private static final long serialVersionUID = 20150528L;
    044
    045    /**
    046     * Factory method to create an unmodifiable set.
    047     *
    048     * @param <E> the element type
    049     * @param set  the set to decorate, must not be null
    050     * @return a new unmodifiable {@link NavigableSet}
    051     * @throws NullPointerException if set is null
    052     */
    053    public static <E> NavigableSet<E> unmodifiableNavigableSet(final NavigableSet<E> set) {
    054        if (set instanceof Unmodifiable) {
    055            return set;
    056        }
    057        return new UnmodifiableNavigableSet<>(set);
    058    }
    059
    060    //-----------------------------------------------------------------------
    061    /**
    062     * Constructor that wraps (not copies).
    063     *
    064     * @param set  the set to decorate, must not be null
    065     * @throws NullPointerException if set is null
    066     */
    067    private UnmodifiableNavigableSet(final NavigableSet<E> set) {
    068        super(set);
    069    }
    070
    071    //-----------------------------------------------------------------------
    072    @Override
    073    public Iterator<E> iterator() {
    074        return UnmodifiableIterator.unmodifiableIterator(decorated().iterator());
    075    }
    076
    077    @Override
    078    public boolean add(final E object) {
    079        throw new UnsupportedOperationException();
    080    }
    081
    082    @Override
    083    public boolean addAll(final Collection<? extends E> coll) {
    084        throw new UnsupportedOperationException();
    085    }
    086
    087    @Override
    088    public void clear() {
    089        throw new UnsupportedOperationException();
    090    }
    091
    092    @Override
    093    public boolean remove(final Object object) {
    094        throw new UnsupportedOperationException();
    095    }
    096
    097    @Override
    098    public boolean removeAll(final Collection<?> coll) {
    099        throw new UnsupportedOperationException();
    100    }
    101
    102    @Override
    103    public boolean retainAll(final Collection<?> coll) {
    104        throw new UnsupportedOperationException();
    105    }
    106
    107    // SortedSet
    108    //-----------------------------------------------------------------------
    109    @Override
    110    public SortedSet<E> subSet(final E fromElement, final E toElement) {
    111        final SortedSet<E> sub = decorated().subSet(fromElement, toElement);
    112        return UnmodifiableSortedSet.unmodifiableSortedSet(sub);
    113    }
    114
    115    @Override
    116    public SortedSet<E> headSet(final E toElement) {
    117        final SortedSet<E> head = decorated().headSet(toElement);
    118        return UnmodifiableSortedSet.unmodifiableSortedSet(head);
    119    }
    120
    121    @Override
    122    public SortedSet<E> tailSet(final E fromElement) {
    123        final SortedSet<E> tail = decorated().tailSet(fromElement);
    124        return UnmodifiableSortedSet.unmodifiableSortedSet(tail);
    125    }
    126
    127    // NavigableSet
    128    //-----------------------------------------------------------------------
    129    @Override
    130    public NavigableSet<E> descendingSet() {
    131        return unmodifiableNavigableSet(decorated().descendingSet());
    132    }
    133
    134    @Override
    135    public Iterator<E> descendingIterator() {
    136        return UnmodifiableIterator.unmodifiableIterator(decorated().descendingIterator());
    137    }
    138
    139    @Override
    140    public NavigableSet<E> subSet(final E fromElement, final boolean fromInclusive, final E toElement,
    141            final boolean toInclusive) {
    142        final NavigableSet<E> sub = decorated().subSet(fromElement, fromInclusive, toElement, toInclusive);
    143        return unmodifiableNavigableSet(sub);
    144    }
    145
    146    @Override
    147    public NavigableSet<E> headSet(final E toElement, final boolean inclusive) {
    148        final NavigableSet<E> head = decorated().headSet(toElement, inclusive);
    149        return unmodifiableNavigableSet(head);
    150    }
    151
    152    @Override
    153    public NavigableSet<E> tailSet(final E fromElement, final boolean inclusive) {
    154        final NavigableSet<E> tail = decorated().tailSet(fromElement, inclusive);
    155        return unmodifiableNavigableSet(tail);
    156    }
    157
    158    //-----------------------------------------------------------------------
    159    /**
    160     * Write the collection out using a custom routine.
    161     *
    162     * @param out  the output stream
    163     * @throws IOException if an error occurs while writing to the stream
    164     */
    165    private void writeObject(final ObjectOutputStream out) throws IOException {
    166        out.defaultWriteObject();
    167        out.writeObject(decorated());
    168    }
    169
    170    /**
    171     * Read the collection in using a custom routine.
    172     *
    173     * @param in  the input stream
    174     * @throws IOException if an error occurs while reading from the stream
    175     * @throws ClassNotFoundException if an object read from the stream can not be loaded
    176     */
    177    @SuppressWarnings("unchecked") // (1) should only fail if input stream is incorrect
    178    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
    179        in.defaultReadObject();
    180        setCollection((Collection<E>) in.readObject()); // (1)
    181    }
    182
    183}