    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 * @param <K> the type of keys
    038 * @param <V> the type of mapped values
    039 * @since 3.0
    040 */
    041public class EntrySetMapIterator<K, V> implements MapIterator<K, V>, ResettableIterator<K> {
    042
    043    private final Map<K, V> map;
    044    private Iterator<Map.Entry<K, V>> iterator;
    045    private Map.Entry<K, V> last;
    046    private boolean canRemove = false;
    047
    048    /**
    049     * Constructor.
    050     *
    051     * @param map  the map to iterate over
    052     */
    053    public EntrySetMapIterator(final Map<K, V> map) {
    054        super();
    055        this.map = map;
    056        this.iterator = map.entrySet().iterator();
    057    }
    058
    059    //-----------------------------------------------------------------------
    060    /**
    061     * Checks to see if there are more entries still to be iterated.
    062     *
    063     * @return <code>true</code> if the iterator has more elements
    064     */
    065    @Override
    066    public boolean hasNext() {
    067        return iterator.hasNext();
    068    }
    069
    070    /**
    071     * Gets the next <em>key</em> from the <code>Map</code>.
    072     *
    073     * @return the next key in the iteration
    074     * @throws java.util.NoSuchElementException if the iteration is finished
    075     */
    076    @Override
    077    public K next() {
    078        last = iterator.next();
    079        canRemove = true;
    080        return last.getKey();
    081    }
    082
    083    //-----------------------------------------------------------------------
    084    /**
    085     * Removes the last returned key from the underlying <code>Map</code>.
    086     * <p>
    087     * This method can be called once per call to <code>next()</code>.
    088     *
    089     * @throws UnsupportedOperationException if remove is not supported by the map
    090     * @throws IllegalStateException if <code>next()</code> has not yet been called
    091     * @throws IllegalStateException if <code>remove()</code> has already been called
    092     *  since the last call to <code>next()</code>
    093     */
    094    @Override
    095    public void remove() {
    096        if (canRemove == false) {
    097            throw new IllegalStateException("Iterator remove() can only be called once after next()");
    098        }
    099        iterator.remove();
    100        last = null;
    101        canRemove = false;
    102    }
    103
    104    //-----------------------------------------------------------------------
    105    /**
    106     * Gets the current key, which is the key returned by the last call
    107     * to <code>next()</code>.
    108     *
    109     * @return the current key
    110     * @throws IllegalStateException if <code>next()</code> has not yet been called
    111     */
    112    @Override
    113    public K getKey() {
    114        if (last == null) {
    115            throw new IllegalStateException("Iterator getKey() can only be called after next() and before remove()");
    116        }
    117        return last.getKey();
    118    }
    119
    120    /**
    121     * Gets the current value, which is the value associated with the last key
    122     * returned by <code>next()</code>.
    123     *
    124     * @return the current value
    125     * @throws IllegalStateException if <code>next()</code> has not yet been called
    126     */
    127    @Override
    128    public V getValue() {
    129        if (last == null) {
    130            throw new IllegalStateException("Iterator getValue() can only be called after next() and before remove()");
    131        }
    132        return last.getValue();
    133    }
    134
    135    /**
    136     * Sets the value associated with the current key.
    137     *
    138     * @param value  the new value
    139     * @return the previous value
    140     * @throws UnsupportedOperationException if setValue is not supported by the map
    141     * @throws IllegalStateException if <code>next()</code> has not yet been called
    142     * @throws IllegalStateException if <code>remove()</code> has been called since the
    143     *  last call to <code>next()</code>
    144     */
    145    @Override
    146    public V setValue(final V value) {
    147        if (last == null) {
    148            throw new IllegalStateException("Iterator setValue() can only be called after next() and before remove()");
    149        }
    150        return last.setValue(value);
    151    }
    152
    153    //-----------------------------------------------------------------------
    154    /**
    155     * Resets the state of the iterator.
    156     */
    157    @Override
    158    public void reset() {
    159        iterator = map.entrySet().iterator();
    160        last = null;
    161        canRemove = false;
    162    }
    163
    164    /**
    165     * Gets the iterator as a String.
    166     *
    167     * @return a string version of the iterator
    168     */
    169    @Override
    170    public String toString() {
    171        if (last != null) {
    172            return "MapIterator[" + getKey() + "=" + getValue() + "]";
    173        }
    174        return "MapIterator[]";
    175    }
    176
    177}