de.dhke.projects.cutil.collections.cow.CopyOnWriteMapEntrySet.java Source code

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Here is the source code for de.dhke.projects.cutil.collections.cow.CopyOnWriteMapEntrySet.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.cow;

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

class CopyOnWriteMapEntrySet<K, V> implements Set<Entry<K, V>> {
    /// </editor-fold>
    private final CopyOnWriteMap<K, V> _cowMap;
    private Map<K, V> _lastBaseMap = null;
    private Set<Entry<K, V>> _cachedEntrySet = null;

    protected CopyOnWriteMapEntrySet(final CopyOnWriteMap<K, V> cowMap) {
        _cowMap = cowMap;
    }

    @Override
    public int size() {
        return getOriginalEntrySet().size();
    }

    @Override
    public boolean isEmpty() {
        return getOriginalEntrySet().isEmpty();
    }

    @Override
    public boolean contains(final Object o) {
        if (o instanceof Map.Entry) {
            Map.Entry<?, ?> entry = (Map.Entry) o;
            if (_cowMap.containsKey(entry.getKey()))
                return _cowMap.get(entry.getKey()).equals(entry.getValue());
            else
                return false;
        } else
            return false;
    }

    @Override
    public Iterator<Entry<K, V>> iterator() {
        return new Itr();
    }

    @Override
    public Object[] toArray() {
        return getOriginalEntrySet().toArray();
    }

    @Override
    public <T> T[] toArray(final T[] a) {
        return getOriginalEntrySet().toArray(a);
    }

    @Override
    public boolean add(final Entry<K, V> e) {
        _cowMap.put(e.getKey(), e.getValue());
        return true;
    }

    @Override
    public boolean remove(final Object o) {
        if (o instanceof Entry) {
            @SuppressWarnings(value = "unchecked")
            Entry<K, V> entry = (Entry<K, V>) o;
            if (_cowMap.containsKey(entry.getKey())) {
                _cowMap.remove(entry.getKey());
                return true;
            } else
                return false;
        } else
            return false;
    }

    @Override
    public boolean containsAll(final Collection<?> c) {
        return getOriginalEntrySet().containsAll(c);
    }

    @Override
    public boolean addAll(final Collection<? extends Entry<K, V>> c) {
        boolean added = false;
        for (Entry<K, V> entry : c) {
            if (add(entry))
                added = true;
        }
        return added;
    }

    @Override
    public boolean retainAll(final Collection<?> c) {
        _cowMap.copy();
        return getOriginalEntrySet().retainAll(c);
    }

    @Override
    public boolean removeAll(final Collection<?> c) {
        _cowMap.copy();
        return getOriginalEntrySet().removeAll(c);
    }

    @Override
    public void clear() {
        _cowMap.copy();
        getOriginalEntrySet().clear();
    }

    @Override
    public boolean equals(final Object obj) {
        if (this == obj)
            return true;
        return _cowMap.equals(obj);
    }

    @Override
    public int hashCode() {
        int hCode = 0;
        for (Entry<K, V> entry : this)
            hCode += entry.hashCode();
        return hCode;
    }

    private Set<Entry<K, V>> getOriginalEntrySet() {
        /* cache entrty set to avoid re-fetch */
        if (_lastBaseMap != _cowMap.getDecoratee()) {
            _lastBaseMap = _cowMap.getDecoratee();
            _cachedEntrySet = _lastBaseMap.entrySet();
        }
        assert _cachedEntrySet != null;
        return _cachedEntrySet;
    }
    /// <editor-fold defaultstate="collapsed" desc="class Itr">

    private class Itr implements Iterator<Map.Entry<K, V>> {

        private final Iterator<K> _keyIterator;
        private final boolean _collectionAlreadyCopied;

        Itr() {
            super();
            _collectionAlreadyCopied = _cowMap.isWasCopied();
            _keyIterator = _cowMap.getDecoratee().keySet().iterator();
        }

        @Override
        public boolean hasNext() {
            return _keyIterator.hasNext();
        }

        @Override
        public Entry<K, V> next() {
            K nextKey = _keyIterator.next();
            V nextValue = _cowMap.get(nextKey);
            return new DefaultMapEntry<>(nextKey, nextValue);
        }

        @Override
        public void remove() {
            /**
             * I cannot think of a proper way to fully support this method. If a COW list has not been copied yet, a
             * remove would change the underlying collection. In this case, we would have to create a new iterator at
             * exactly the same position for the new collection. This works for lists but not for collections.
             *
             */
            if (_collectionAlreadyCopied)
                _keyIterator.remove();
            else
                throw new UnsupportedOperationException(
                        "Cannot remove from untouched CopyOnWriteMap via iterator.");
        }
    }
}