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.iterators;
018
019import org.apache.commons.collections4.MapIterator;
020import org.apache.commons.collections4.Unmodifiable;
021
022/**
023 * Decorates a map iterator such that it cannot be modified.
024 * <p>
025 * Attempts to modify it will result in an UnsupportedOperationException.
026 * </p>
027 *
028 * @param <K> the type of keys
029 * @param <V> the type of mapped values
030 * @since 3.0
031 */
032public final class UnmodifiableMapIterator<K, V> implements MapIterator<K, V>, Unmodifiable {
033
034    /** The iterator being decorated */
035    private final MapIterator<? extends K, ? extends V> iterator;
036
037    //-----------------------------------------------------------------------
038    /**
039     * Decorates the specified iterator such that it cannot be modified.
040     *
041     * @param <K>  the key type
042     * @param <V>  the value type
043     * @param iterator  the iterator to decorate
044     * @return a new unmodifiable map iterator
045     * @throws NullPointerException if the iterator is null
046     */
047    public static <K, V> MapIterator<K, V> unmodifiableMapIterator(
048            final MapIterator<? extends K, ? extends V> iterator) {
049        if (iterator == null) {
050            throw new NullPointerException("MapIterator must not be null");
051        }
052        if (iterator instanceof Unmodifiable) {
053            @SuppressWarnings("unchecked") // safe to upcast
054            final MapIterator<K, V> tmpIterator = (MapIterator<K, V>) iterator;
055            return tmpIterator;
056        }
057        return new UnmodifiableMapIterator<>(iterator);
058    }
059
060    //-----------------------------------------------------------------------
061    /**
062     * Constructor.
063     *
064     * @param iterator  the iterator to decorate
065     */
066    private UnmodifiableMapIterator(final MapIterator<? extends K, ? extends V> iterator) {
067        super();
068        this.iterator = iterator;
069    }
070
071    //-----------------------------------------------------------------------
072    @Override
073    public boolean hasNext() {
074        return iterator.hasNext();
075    }
076
077    @Override
078    public K next() {
079        return iterator.next();
080    }
081
082    @Override
083    public K getKey() {
084        return iterator.getKey();
085    }
086
087    @Override
088    public V getValue() {
089        return iterator.getValue();
090    }
091
092    @Override
093    public V setValue(final V value) {
094        throw new UnsupportedOperationException("setValue() is not supported");
095    }
096
097    @Override
098    public void remove() {
099        throw new UnsupportedOperationException("remove() is not supported");
100    }
101
102}