de.dhke.projects.cutil.collections.iterator.MultiMapEntryIterator.java Source code

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Here is the source code for de.dhke.projects.cutil.collections.iterator.MultiMapEntryIterator.java

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/**
 * (c) 2009-2014 Peter Wullinger
 *
 * $Id$
 *
 * Use, modification and restribution of this file are covered by the
 * terms of the Artistic License 2.0.
 *
 * You should have received a copy of the license terms in a file named
 * "LICENSE" together with this software package.
 *
 * Disclaimer of Warranty: THE PACKAGE IS PROVIDED BY THE COPYRIGHT
 * HOLDER AND CONTRIBUTORS "AS IS' AND WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTIES. THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR
 * A PARTICULAR PURPOSE, OR NON-INFRINGEMENT ARE DISCLAIMED TO THE
 * EXTENT PERMITTED BY YOUR LOCAL LAW. UNLESS REQUIRED BY LAW, NO
 * COPYRIGHT HOLDER OR CONTRIBUTOR WILL BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING IN ANY WAY OUT
 * OF THE USE OF THE PACKAGE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 **/
package de.dhke.projects.cutil.collections.iterator;

import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.NoSuchElementException;
import org.apache.commons.collections15.MultiMap;
import org.apache.commons.collections15.keyvalue.DefaultMapEntry;

/**
 *
 * @param <K> 
 * @param <V> 
 * @author Peter Wullinger <java@dhke.de>
 */
public class MultiMapEntryIterator<K, V> implements Iterator<Map.Entry<K, V>> {

    private final Iterator<Map.Entry<K, Collection<V>>> _baseIter;
    private K _currentKey;
    /* the current value collection. {@literal null} if we reached the end of the map */
    private Iterator<V> _currentValueCollection;
    private Map.Entry<K, V> _currentEntry;

    protected MultiMapEntryIterator(final MultiMap<K, V> baseMap) {
        this(baseMap.entrySet());
    }

    protected MultiMapEntryIterator(final Iterable<Map.Entry<K, Collection<V>>> baseIterable) {
        _baseIter = baseIterable.iterator();
        /* advance to first value collection */
        if (_baseIter.hasNext()) {
            final Map.Entry<K, Collection<V>> entry = _baseIter.next();
            _currentKey = entry.getKey();
            _currentValueCollection = entry.getValue().iterator();
        }
        advance();
    }

    public static <K, V> MultiMapEntryIterator<K, V> decorate(final MultiMap<K, V> baseMap) {
        return new MultiMapEntryIterator<>(baseMap.entrySet());
    }

    public static <K, V> MultiMapEntryIterator<K, V> decorate(
            final Iterable<Map.Entry<K, Collection<V>>> baseIterable) {
        return new MultiMapEntryIterator<>(baseIterable);
    }

    @Override
    public boolean hasNext() {
        return _currentEntry != null;
    }

    @Override
    public Entry<K, V> next() {
        final Entry<K, V> currentEntry = advance();
        if (currentEntry == null)
            throw new NoSuchElementException("No more multimap entries");
        else
            return currentEntry;
    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException("Not supported yet.");
    }

    private Map.Entry<K, V> advance() {
        Map.Entry<K, V> currentEntry = _currentEntry;
        if (_currentValueCollection != null) {
            assert _currentKey != null;
            if (_currentValueCollection.hasNext()) {
                final V currentValue = _currentValueCollection.next();
                _currentEntry = new DefaultMapEntry<>(_currentKey, currentValue);
            } else {
                _currentEntry = null;
                while ((_baseIter.hasNext()) && (_currentValueCollection != null) && (_currentEntry == null)) {
                    final Map.Entry<K, Collection<V>> nextMapEntry = _baseIter.next();
                    _currentKey = nextMapEntry.getKey();
                    if (nextMapEntry.getValue() != null) {
                        _currentValueCollection = nextMapEntry.getValue().iterator();
                        if (_currentValueCollection.hasNext()) {
                            final V currentValue = _currentValueCollection.next();
                            _currentEntry = new DefaultMapEntry<>(_currentKey, currentValue);
                        }
                    }
                }
            }
        }
        return currentEntry;
    }
}