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.list;
018
019import java.util.Collection;
020import java.util.Iterator;
021import java.util.List;
022import java.util.ListIterator;
023
024import org.apache.commons.collections4.Unmodifiable;
025import org.apache.commons.collections4.iterators.UnmodifiableIterator;
026import org.apache.commons.collections4.iterators.UnmodifiableListIterator;
027
028/**
029 * Decorates another <code>List</code> to ensure it can't be altered.
030 * <p>
031 * This class is Serializable from Commons Collections 3.1.
032 * <p>
033 * Attempts to modify it will result in an UnsupportedOperationException.
034 *
035 * @since 3.0
036 */
037public final class UnmodifiableList<E>
038        extends AbstractSerializableListDecorator<E>
039        implements Unmodifiable {
040
041    /** Serialization version */
042    private static final long serialVersionUID = 6595182819922443652L;
043
044    /**
045     * Factory method to create an unmodifiable list.
046     *
047     * @param <E> the type of the elements in the list
048     * @param list  the list to decorate, must not be null
049     * @return a new unmodifiable list
050     * @throws NullPointerException if list is null
051     * @since 4.0
052     */
053    public static <E> List<E> unmodifiableList(final List<? extends E> list) {
054        if (list instanceof Unmodifiable) {
055            @SuppressWarnings("unchecked") // safe to upcast
056            final List<E> tmpList = (List<E>) list;
057            return tmpList;
058        }
059        return new UnmodifiableList<>(list);
060    }
061
062    //-----------------------------------------------------------------------
063    /**
064     * Constructor that wraps (not copies).
065     *
066     * @param list  the list to decorate, must not be null
067     * @throws NullPointerException if list is null
068     */
069    @SuppressWarnings("unchecked") // safe to upcast
070    public UnmodifiableList(final List<? extends E> list) {
071        super((List<E>) list);
072    }
073
074    //-----------------------------------------------------------------------
075    @Override
076    public Iterator<E> iterator() {
077        return UnmodifiableIterator.unmodifiableIterator(decorated().iterator());
078    }
079
080    @Override
081    public boolean add(final Object object) {
082        throw new UnsupportedOperationException();
083    }
084
085    @Override
086    public boolean addAll(final Collection<? extends E> coll) {
087        throw new UnsupportedOperationException();
088    }
089
090    @Override
091    public void clear() {
092        throw new UnsupportedOperationException();
093    }
094
095    @Override
096    public boolean remove(final Object object) {
097        throw new UnsupportedOperationException();
098    }
099
100    @Override
101    public boolean removeAll(final Collection<?> coll) {
102        throw new UnsupportedOperationException();
103    }
104
105    @Override
106    public boolean retainAll(final Collection<?> coll) {
107        throw new UnsupportedOperationException();
108    }
109
110    //-----------------------------------------------------------------------
111    @Override
112    public ListIterator<E> listIterator() {
113        return UnmodifiableListIterator.umodifiableListIterator(decorated().listIterator());
114    }
115
116    @Override
117    public ListIterator<E> listIterator(final int index) {
118        return UnmodifiableListIterator.umodifiableListIterator(decorated().listIterator(index));
119    }
120
121    @Override
122    public void add(final int index, final E object) {
123        throw new UnsupportedOperationException();
124    }
125
126    @Override
127    public boolean addAll(final int index, final Collection<? extends E> coll) {
128        throw new UnsupportedOperationException();
129    }
130
131    @Override
132    public E remove(final int index) {
133        throw new UnsupportedOperationException();
134    }
135
136    @Override
137    public E set(final int index, final E object) {
138        throw new UnsupportedOperationException();
139    }
140
141    @Override
142    public List<E> subList(final int fromIndex, final int toIndex) {
143        final List<E> sub = decorated().subList(fromIndex, toIndex);
144        return new UnmodifiableList<>(sub);
145    }
146
147}