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 java.util.Iterator;
020import java.util.Map;
021
022import org.apache.commons.collections4.MapIterator;
023import org.apache.commons.collections4.ResettableIterator;
024
025/**
026 * Implements a <code>MapIterator</code> using a Map entrySet.
027 * Reverse iteration is not supported.
028 * <pre>
029 * MapIterator it = map.mapIterator();
030 * while (it.hasNext()) {
031 *   Object key = it.next();
032 *   Object value = it.getValue();
033 *   it.setValue(newValue);
034 * }
035 * </pre>
036 *
037 * @since 3.0
038 */
039public class EntrySetMapIterator<K, V> implements MapIterator<K, V>, ResettableIterator<K> {
040
041    private final Map<K, V> map;
042    private Iterator<Map.Entry<K, V>> iterator;
043    private Map.Entry<K, V> last;
044    private boolean canRemove = false;
045
046    /**
047     * Constructor.
048     *
049     * @param map  the map to iterate over
050     */
051    public EntrySetMapIterator(final Map<K, V> map) {
052        super();
053        this.map = map;
054        this.iterator = map.entrySet().iterator();
055    }
056
057    //-----------------------------------------------------------------------
058    /**
059     * Checks to see if there are more entries still to be iterated.
060     *
061     * @return <code>true</code> if the iterator has more elements
062     */
063    @Override
064    public boolean hasNext() {
065        return iterator.hasNext();
066    }
067
068    /**
069     * Gets the next <em>key</em> from the <code>Map</code>.
070     *
071     * @return the next key in the iteration
072     * @throws java.util.NoSuchElementException if the iteration is finished
073     */
074    @Override
075    public K next() {
076        last = iterator.next();
077        canRemove = true;
078        return last.getKey();
079    }
080
081    //-----------------------------------------------------------------------
082    /**
083     * Removes the last returned key from the underlying <code>Map</code>.
084     * <p>
085     * This method can be called once per call to <code>next()</code>.
086     *
087     * @throws UnsupportedOperationException if remove is not supported by the map
088     * @throws IllegalStateException if <code>next()</code> has not yet been called
089     * @throws IllegalStateException if <code>remove()</code> has already been called
090     *  since the last call to <code>next()</code>
091     */
092    @Override
093    public void remove() {
094        if (canRemove == false) {
095            throw new IllegalStateException("Iterator remove() can only be called once after next()");
096        }
097        iterator.remove();
098        last = null;
099        canRemove = false;
100    }
101
102    //-----------------------------------------------------------------------
103    /**
104     * Gets the current key, which is the key returned by the last call
105     * to <code>next()</code>.
106     *
107     * @return the current key
108     * @throws IllegalStateException if <code>next()</code> has not yet been called
109     */
110    @Override
111    public K getKey() {
112        if (last == null) {
113            throw new IllegalStateException("Iterator getKey() can only be called after next() and before remove()");
114        }
115        return last.getKey();
116    }
117
118    /**
119     * Gets the current value, which is the value associated with the last key
120     * returned by <code>next()</code>.
121     *
122     * @return the current value
123     * @throws IllegalStateException if <code>next()</code> has not yet been called
124     */
125    @Override
126    public V getValue() {
127        if (last == null) {
128            throw new IllegalStateException("Iterator getValue() can only be called after next() and before remove()");
129        }
130        return last.getValue();
131    }
132
133    /**
134     * Sets the value associated with the current key.
135     *
136     * @param value  the new value
137     * @return the previous value
138     * @throws UnsupportedOperationException if setValue is not supported by the map
139     * @throws IllegalStateException if <code>next()</code> has not yet been called
140     * @throws IllegalStateException if <code>remove()</code> has been called since the
141     *  last call to <code>next()</code>
142     */
143    @Override
144    public V setValue(final V value) {
145        if (last == null) {
146            throw new IllegalStateException("Iterator setValue() can only be called after next() and before remove()");
147        }
148        return last.setValue(value);
149    }
150
151    //-----------------------------------------------------------------------
152    /**
153     * Resets the state of the iterator.
154     */
155    @Override
156    public void reset() {
157        iterator = map.entrySet().iterator();
158        last = null;
159        canRemove = false;
160    }
161
162    /**
163     * Gets the iterator as a String.
164     *
165     * @return a string version of the iterator
166     */
167    @Override
168    public String toString() {
169        if (last != null) {
170            return "MapIterator[" + getKey() + "=" + getValue() + "]";
171        }
172        return "MapIterator[]";
173    }
174
175}