public CollectionBag(final Bag<E> bag) {
        super(bag);
    }

    /**
     * <i>(Change)</i>
     * Adds one copy of the specified object to the Bag.
     * <p>
     * Since this method always increases the size of the bag, it
     * will always return {@code true}.
     *
     * @param object  the object to add
     * @return {@code true}, always
     */
    @Override
    public boolean add(final E object) {
        return add(object, 1);
    }

    /**
     * <i>(Change)</i>
     * Adds {@code count} copies of the specified object to the Bag.
     * <p>
     * Since this method always increases the size of the bag, it
     * will always return {@code true}.
     *
     * @param object  the object to add
     * @param count  the number of copies to add
     * @return {@code true}, always
     */
    @Override
    public boolean add(final E object, final int count) {
        decorated().add(object, count);
        return true;
    }

    // Collection interface

    @Override
    public boolean addAll(final Collection<? extends E> coll) {
        boolean changed = false;
        for (final E current : coll) {
            final boolean added = add(current, 1);
            changed = changed || added;
        }
        return changed;
    }

    /**
     * <i>(Change)</i>
     * Returns {@code true} if the bag contains all elements in
     * the given collection, <b>not</b> respecting cardinality. That is,
     * if the given collection {@code coll} contains at least one of
     * every object contained in this object.
     *
     * @param coll  the collection to check against
     * @return {@code true} if the Bag contains at least one of every object in the collection
     */
    @Override
    public boolean containsAll(final Collection<?> coll) {
        return coll.stream().allMatch(this::contains);
    }

    /**
     * Read the collection in using a custom routine.
     *
     * @param in  the input stream
     * @throws IOException if an error occurs while reading from the stream
     * @throws ClassNotFoundException if an object read from the stream can not be loaded
     * @throws ClassCastException if deserialized object has wrong type
     */
    @SuppressWarnings("unchecked") // will throw CCE, see Javadoc
    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
        in.defaultReadObject();
        setCollection((Collection<E>) in.readObject());
    }

    /**
     * <i>(Change)</i>
     * Removes the first occurrence of the given object from the bag.
     * <p>
     * This will also remove the object from the {@link #uniqueSet()} if the
     * bag contains no occurrence anymore of the object after this operation.
     *
     * @param object  the object to remove
     * @return {@code true} if this call changed the collection
     */
    @Override
    public boolean remove(final Object object) {
        return remove(object, 1);
    }

    /**
     * <i>(Change)</i>
     * Remove all elements represented in the given collection,
     * <b>not</b> respecting cardinality. That is, remove <i>all</i>
     * occurrences of every object contained in the given collection.
     *
     * @param coll  the collection to remove
     * @return {@code true} if this call changed the collection
     */
    @Override
    public boolean removeAll(final Collection<?> coll) {
        if (coll != null) {
            boolean result = false;
            for (final Object obj : coll) {
                final boolean changed = remove(obj, getCount(obj));
                result = result || changed;
            }
            return result;
        }
        // let the decorated bag handle the case of null argument
        return decorated().removeAll(null);
    }

    /**
     * <i>(Change)</i>
     * Remove any members of the bag that are not in the given collection,
     * <i>not</i> respecting cardinality. That is, any object in the given
     * collection {@code coll} will be retained in the bag with the same
     * number of copies prior to this operation. All other objects will be
     * completely removed from this bag.
     * <p>
     * This implementation iterates over the elements of this bag, checking
     * each element in turn to see if it's contained in {@code coll}.
     * If it's not contained, it's removed from this bag. As a consequence,
     * it is advised to use a collection type for {@code coll} that provides
     * a fast (e.g. O(1)) implementation of {@link Collection#contains(Object)}.
     *
     * @param coll  the collection to retain
     * @return {@code true} if this call changed the collection
     */
    @Override
    public boolean retainAll(final Collection<?> coll) {
        if (coll != null) {
            boolean modified = false;
            final Iterator<E> e = iterator();
            while (e.hasNext()) {
                if (!coll.contains(e.next())) {
                    e.remove();
                    modified = true;
                }
            }
            return modified;
        }
        // let the decorated bag handle the case of null argument
        return decorated().retainAll(null);
    }

    // Bag interface

    /**
     * Write the collection out using a custom routine.
     *
     * @param out  the output stream
     * @throws IOException if an error occurs while writing to the stream
     */
    private void writeObject(final ObjectOutputStream out) throws IOException {
        out.defaultWriteObject();
        out.writeObject(decorated());
    }

}

for (final Collection<E> item : all) {
            size += item.size();
        }
        return size;
    }

    /**
     * Returns an array containing all of the elements in this composite.
     *
     * @return an object array of all the elements in the collection
     */
    @Override
    public Object[] toArray() {
        final Object[] result = new Object[size()];
        int i = 0;
        for (final Iterator<E> it = iterator(); it.hasNext(); i++) {
            result[i] = it.next();
        }
        return result;
    }

    /**
     * Returns an object array, populating the supplied array if possible.
     * See {@code Collection} interface for full details.
     *
     * @param <T>  the type of the elements in the collection
     * @param array  the array to use, populating if possible
     * @return an array of all the elements in the collection
     */
    @Override
    @SuppressWarnings("unchecked")
    public <T> T[] toArray(final T[] array) {
        final int size = size();
        Object[] result = null;
        if (array.length >= size) {
            result = array;
        } else {
            result = (Object[]) Array.newInstance(array.getClass().getComponentType(), size);
        }

        int offset = 0;
        for (final Collection<E> item : all) {
            for (final E e : item) {
                result[offset++] = e;
            }
        }
        if (result.length > size) {
            result[size] = null;
        }
        return (T[]) result;
    }

    /**
     * Returns a new collection containing all of the elements
     *
     * @return A new ArrayList containing all of the elements in this composite.
     *         The new collection is <i>not</i> backed by this composite.
     */
    public Collection<E> toCollection() {

BagIterator(final AbstractMapBag<E> parent) {
            this.parent = parent;
            this.entryIterator = parent.map.entrySet().iterator();
            this.current = null;
            this.mods = parent.modCount;
            this.canRemove = false;
        }

        /** {@inheritDoc} */
        @Override
        public boolean hasNext() {
            return itemCount > 0 || entryIterator.hasNext();
        }

        /** {@inheritDoc} */
        @Override
        public E next() {
            if (parent.modCount != mods) {
                throw new ConcurrentModificationException();
            }
            if (itemCount == 0) {
                current = entryIterator.next();
                itemCount = current.getValue().value;
            }
            canRemove = true;
            itemCount--;
            return current.getKey();
        }

        /** {@inheritDoc} */
        @Override
        public void remove() {
            if (parent.modCount != mods) {
                throw new ConcurrentModificationException();
            }
            if (!canRemove) {
                throw new IllegalStateException();
            }
            final MutableInteger mut = current.getValue();
            if (mut.value > 1) {
                mut.value--;
            } else {
                entryIterator.remove();
            }
            parent.size--;
            canRemove = false;
        }
    }
    /**
     * Mutable integer class for storing the data.
     */
    protected static class MutableInteger {

decorated().clear();
    }

    @Override
    public boolean containsKey(final Object key) {
        return decorated().containsKey(key);
    }

    @Override
    public boolean containsValue(final Object value) {
        return decorated().containsValue(value);
    }

    /**
     * Gets the map being decorated.
     *
     * @return the decorated map
     */
    protected Map<K, V> decorated() {
        return map;
    }

    @Override
    public Set<Map.Entry<K, V>> entrySet() {
        return decorated().entrySet();
    }

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

    @Override
    public V get(final Object key) {
        return decorated().get(key);
    }

    @Override
    public int hashCode() {
        return decorated().hashCode();
    }

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

    @Override
    public Set<K> keySet() {
        return decorated().keySet();
    }

    @Override
    public V put(final K key, final V value) {

return UnmodifiableIterator.<E>unmodifiableIterator(decorated().iterator());
    }

    /**
     * Read the collection in using a custom routine.
     *
     * @param in  the input stream
     * @throws IOException if an error occurs while reading from the stream
     * @throws ClassNotFoundException if an object read from the stream can not be loaded
     * @throws ClassCastException if deserialized object has wrong type
     */
    @SuppressWarnings("unchecked") // will throw CCE, see Javadoc
    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
        in.defaultReadObject();
        setCollection((Collection<E>) in.readObject());
    }

    @Override
    public boolean remove(final Object object) {
        throw new UnsupportedOperationException();
    }

    @Override
    public boolean remove(final Object object, final int count) {
        throw new UnsupportedOperationException();
    }

    @Override
    public boolean removeAll(final Collection<?> coll) {
        throw new UnsupportedOperationException();
    }

    /**
     * @since 4.4
     */
    @Override
    public boolean removeIf(final Predicate<? super E> filter) {
        throw new UnsupportedOperationException();
    }

    @Override
    public boolean retainAll(final Collection<?> coll) {
        throw new UnsupportedOperationException();
    }

    @Override
    public Set<E> uniqueSet() {
        final Set<E> set = decorated().uniqueSet();
        return UnmodifiableSet.<E>unmodifiableSet(set);

inverse = new UnmodifiableOrderedBidiMap<>(decorated().inverseBidiMap());
            inverse.inverse = this;
        }
        return inverse;
    }

    @Override
    public Set<K> keySet() {
        final Set<K> set = super.keySet();
        return UnmodifiableSet.unmodifiableSet(set);
    }

    @Override
    public OrderedMapIterator<K, V> mapIterator() {
        final OrderedMapIterator<K, V> it = decorated().mapIterator();
        return UnmodifiableOrderedMapIterator.unmodifiableOrderedMapIterator(it);
    }

    @Override
    public V put(final K key, final V value) {
        throw new UnsupportedOperationException();
    }

    @Override
    public void putAll(final Map<? extends K, ? extends V> mapToCopy) {
        throw new UnsupportedOperationException();
    }

    @Override
    public V remove(final Object key) {
        throw new UnsupportedOperationException();
    }

    @Override
    public K removeValue(final Object value) {
        throw new UnsupportedOperationException();
    }

    @Override
    public Set<V> values() {

return UnmodifiableMapIterator.unmodifiableMapIterator(it);
    }

    @Override
    public V put(final K key, final V value) {
        throw new UnsupportedOperationException();
    }

    @Override
    public void putAll(final Map<? extends K, ? extends V> mapToCopy) {
        throw new UnsupportedOperationException();
    }

    /**
     * Read the map in using a custom routine.
     *
     * @param in  the input stream
     * @throws IOException if an error occurs while reading from the stream
     * @throws ClassNotFoundException if an object read from the stream can not be loaded
     * @since 3.1
     */
    @SuppressWarnings("unchecked")
    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
        in.defaultReadObject();
        map = (Map<K, V>) in.readObject();
    }

    @Override
    public V remove(final Object key) {
        throw new UnsupportedOperationException();
    }

    @Override
    public Collection<V> values() {
        final Collection<V> coll = super.values();
        return UnmodifiableCollection.unmodifiableCollection(coll);
    }

    /**
     * Write the map out using a custom routine.
     *
     * @param out  the output stream
     * @throws IOException if an error occurs while writing to the stream
     * @since 3.1
     */
    private void writeObject(final ObjectOutputStream out) throws IOException {
        out.defaultWriteObject();
        out.writeObject(map);
    }

}

super((Collection<E>) coll);
    }

    @Override
    public boolean add(final E object) {
        throw new UnsupportedOperationException();
    }

    @Override
    public boolean addAll(final Collection<? extends E> coll) {
        throw new UnsupportedOperationException();
    }

    @Override
    public void clear() {
        throw new UnsupportedOperationException();
    }

    @Override
    public Iterator<E> iterator() {
        return UnmodifiableIterator.unmodifiableIterator(decorated().iterator());
    }

    @Override
    public boolean remove(final Object object) {
        throw new UnsupportedOperationException();
    }

    @Override
    public boolean removeAll(final Collection<?> coll) {
        throw new UnsupportedOperationException();
    }

    /**
     * @since 4.4
     */
    @Override
    public boolean removeIf(final Predicate<? super E> filter) {
        throw new UnsupportedOperationException();
    }

    @Override
    public boolean retainAll(final Collection<?> coll) {
        throw new UnsupportedOperationException();
    }

}

return it.hasNext() && CollectionUtils.addAll(get(key), it);
    }

    /**
     * Copies all of the mappings from the specified map to this map. The effect
     * of this call is equivalent to that of calling {@link #put(Object,Object)
     * put(k, v)} on this map once for each mapping from key {@code k} to value
     * {@code v} in the specified map. The behavior of this operation is
     * undefined if the specified map is modified while the operation is in
     * progress.
     *
     * @param map mappings to be stored in this map, may not be null
     * @return true if the map changed as a result of this operation
     * @throws NullPointerException if map is null
     */
    @Override
    public boolean putAll(final Map<? extends K, ? extends V> map) {
        Objects.requireNonNull(map, "map");
        boolean changed = false;
        for (final Map.Entry<? extends K, ? extends V> entry : map.entrySet()) {
            changed |= put(entry.getKey(), entry.getValue());
        }
        return changed;
    }

    /**
     * Copies all of the mappings from the specified MultiValuedMap to this map.
     * The effect of this call is equivalent to that of calling
     * {@link #put(Object,Object) put(k, v)} on this map once for each mapping
     * from key {@code k} to value {@code v} in the specified map. The
     * behavior of this operation is undefined if the specified map is modified
     * while the operation is in progress.
     *
     * @param map mappings to be stored in this map, may not be null
     * @return true if the map changed as a result of this operation
     * @throws NullPointerException if map is null
     */
    @Override
    public boolean putAll(final MultiValuedMap<? extends K, ? extends V> map) {
        Objects.requireNonNull(map, "map");
        boolean changed = false;
        for (final Map.Entry<? extends K, ? extends V> entry : map.entries()) {
            changed |= put(entry.getKey(), entry.getValue());
        }
        return changed;
    }

return decorated().addAll(index, coll);
    }

    /**
     * Gets the list being decorated.
     *
     * @return the decorated list
     */
    @Override
    protected List<E> decorated() {
        return (List<E>) super.decorated();
    }

    @Override
    public boolean equals(final Object object) {
        return object == this || decorated().equals(object);
    }

    @Override
    public E get(final int index) {
        return decorated().get(index);
    }

    @Override
    public int hashCode() {
        return decorated().hashCode();
    }

    @Override
    public int indexOf(final Object object) {
        return decorated().indexOf(object);
    }

    @Override
    public int lastIndexOf(final Object object) {
        return decorated().lastIndexOf(object);
    }

    @Override
    public ListIterator<E> listIterator() {
        return decorated().listIterator();

return decorated().add(object, count);
    }

    /**
     * Gets the bag being decorated.
     *
     * @return the decorated bag
     */
    @Override
    protected Bag<E> decorated() {
        return (Bag<E>) super.decorated();
    }

    @Override
    public boolean equals(final Object object) {
        return object == this || decorated().equals(object);
    }

    @Override
    public int getCount(final Object object) {
        return decorated().getCount(object);
    }

    @Override
    public int hashCode() {
        return decorated().hashCode();
    }

    @Override
    public boolean remove(final Object object, final int count) {
        return decorated().remove(object, count);
    }

    @Override
    public Set<E> uniqueSet() {
        return decorated().uniqueSet();
    }

}

this.iterator = parent.normalMap.entrySet().iterator();
        }

        @Override
        public K getKey() {
            if (last == null) {
                throw new IllegalStateException(
                        "Iterator getKey() can only be called after next() and before remove()");
            }
            return last.getKey();
        }

        @Override
        public V getValue() {
            if (last == null) {
                throw new IllegalStateException(
                        "Iterator getValue() can only be called after next() and before remove()");
            }
            return last.getValue();
        }

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

        @Override
        public K next() {
            last = iterator.next();
            canRemove = true;
            return last.getKey();
        }

        @Override
        public void remove() {
            if (!canRemove) {
                throw new IllegalStateException("Iterator remove() can only be called once after next()");
            }

return predicatedNavigableSet(head, predicate);
    }

    @Override
    public E higher(final E e) {
        return decorated().higher(e);
    }

    @Override
    public E lower(final E e) {
        return decorated().lower(e);
    }

    @Override
    public E pollFirst() {
        return decorated().pollFirst();
    }

    @Override
    public E pollLast() {
        return decorated().pollLast();
    }

    @Override
    public NavigableSet<E> subSet(final E fromElement, final boolean fromInclusive, final E toElement,
            final boolean toInclusive) {
        final NavigableSet<E> sub = decorated().subSet(fromElement, fromInclusive, toElement, toInclusive);
        return predicatedNavigableSet(sub, predicate);

public Set<Entry<E>> entrySet() {
        return decorated().entrySet();
    }

    @Override
    public boolean equals(final Object object) {
        return object == this || decorated().equals(object);
    }

    @Override
    public int getCount(final Object object) {
        return decorated().getCount(object);
    }

    @Override
    public int hashCode() {
        return decorated().hashCode();
    }

    @Override
    public int remove(final Object object, final int count) {
        return decorated().remove(object, count);
    }

    @Override
    public int setCount(final E object, final int count) {

throw new UnsupportedOperationException();
    }

    /**
     * Read the collection in using a custom routine.
     *
     * @param in  the input stream
     * @throws IOException if an error occurs while reading from the stream
     * @throws ClassNotFoundException if an object read from the stream can not be loaded
     */
    @SuppressWarnings("unchecked") // (1) should only fail if input stream is incorrect
    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
        in.defaultReadObject();
        setCollection((Collection<E>) in.readObject()); // (1)
    }

    @Override
    public boolean remove(final Object object) {
        throw new UnsupportedOperationException();
    }

    @Override
    public boolean removeAll(final Collection<?> coll) {
        throw new UnsupportedOperationException();
    }

    /**
     * @since 4.4
     */
    @Override
    public boolean removeIf(final Predicate<? super E> filter) {
        throw new UnsupportedOperationException();
    }

    @Override
    public boolean retainAll(final Collection<?> coll) {
        throw new UnsupportedOperationException();
    }

    @Override
    public NavigableSet<E> subSet(final E fromElement, final boolean fromInclusive, final E toElement,

final Bag<?> other = (Bag<?>) object;
        if (other.size() != size()) {
            return false;
        }
        for (final E element : map.keySet()) {
            if (other.getCount(element) != getCount(element)) {
                return false;
            }
        }
        return true;
    }

    /**
     * Returns the number of occurrence of the given element in this bag by
     * looking up its count in the underlying map.
     *
     * @param object the object to search for
     * @return the number of occurrences of the object, zero if not found
     */
    @Override
    public int getCount(final Object object) {
        final MutableInteger count = map.get(object);
        if (count != null) {
            return count.value;
        }
        return 0;
    }

    /**
     * Utility method for implementations to access the map that backs this bag.
     * Not intended for interactive use outside of subclasses.
     *
     * @return the map being used by the Bag
     */
    protected Map<E, MutableInteger> getMap() {
        return map;
    }

    /**
     * Gets a hash code for the Bag compatible with the definition of equals.
     * The hash code is defined as the sum total of a hash code for each
     * element. The per element hash code is defined as
     * {@code (e==null ? 0 : e.hashCode()) ^ noOccurrences)}. This hash code
     * is compatible with the Set interface.
     *
     * @return the hash code of the Bag
     */
    @Override
    public int hashCode() {
        int total = 0;
        for (final Entry<E, MutableInteger> entry : map.entrySet()) {

}

    /**
     * Compares this {@code Map.Entry} with another {@code Map.Entry}.
     * <p>
     * Implemented per API documentation of {@link java.util.Map.Entry#equals(Object)}
     *
     * @param obj  the object to compare to
     * @return true if equal key and value
     */
    @Override
    public boolean equals(final Object obj) {
        if (obj == this) {
            return true;
        }
        if (!(obj instanceof Map.Entry)) {
            return false;
        }
        final Map.Entry<?, ?> other = (Map.Entry<?, ?>) obj;
        return
            (getKey() == null ? other.getKey() == null : getKey().equals(other.getKey())) &&
            (getValue() == null ? other.getValue() == null : getValue().equals(other.getValue()));
    }

    /**
     * Gets a hashCode compatible with the equals method.
     * <p>
     * Implemented per API documentation of {@link java.util.Map.Entry#hashCode()}
     *
     * @return a suitable hash code
     */
    @Override

return UnmodifiableMapIterator.unmodifiableMapIterator(it);
    }

    @Override
    public V put(final K key, final V value) {
        throw new UnsupportedOperationException();
    }

    @Override
    public void putAll(final Map<? extends K, ? extends V> mapToCopy) {
        throw new UnsupportedOperationException();
    }

    @Override
    public V remove(final Object key) {
        throw new UnsupportedOperationException();
    }

    @Override
    public K removeValue(final Object value) {
        throw new UnsupportedOperationException();
    }

    @Override
    public Set<V> values() {
        final Set<V> set = super.values();
        return UnmodifiableSet.unmodifiableSet(set);
    }

}

super(sub.parent, startIndex + sub.offset);
            this.sub = sub;
        }

        @Override
        public void add(final E obj) {
            super.add(obj);
            sub.expectedModCount = parent.modCount;
            sub.size++;
        }

        @Override
        public boolean hasNext() {
            return nextIndex() < sub.size;
        }

        @Override
        public boolean hasPrevious() {
            return previousIndex() >= 0;
        }

        @Override
        public int nextIndex() {
            return super.nextIndex() - sub.offset;
        }

        @Override
        public void remove() {
            super.remove();
            sub.expectedModCount = parent.modCount;
            sub.size--;
        }
    }

final Map.Entry<?, ?> other = (Map.Entry<?, ?>) obj;
        return
            (getKey() == null ? other.getKey() == null : getKey().equals(other.getKey())) &&
            (getValue() == null ? other.getValue() == null : getValue().equals(other.getValue()));
    }

    /**
     * Gets a hashCode compatible with the equals method.
     * <p>
     * Implemented per API documentation of {@link java.util.Map.Entry#hashCode()}
     *
     * @return a suitable hash code
     */
    @Override
    public int hashCode() {
        return (getKey() == null ? 0 : getKey().hashCode()) ^
               (getValue() == null ? 0 : getValue().hashCode());
    }

    /**
     * Sets the value stored in this {@code Map.Entry}.
     * <p>
     * This {@code Map.Entry} is not connected to a Map, so only the
     * local data is changed.
     *
     * @param value  the new value
     * @return the previous value
     */
    @Override
    public V setValue(final V value) { // NOPMD

protected HashMapIterator(final AbstractHashedMap<K, V> parent) {
            super(parent);
        }

        @Override
        public K getKey() {
            final HashEntry<K, V> current = currentEntry();
            if (current == null) {
                throw new IllegalStateException(AbstractHashedMap.GETKEY_INVALID);
            }
            return current.getKey();
        }

        @Override
        public V getValue() {
            final HashEntry<K, V> current = currentEntry();
            if (current == null) {
                throw new IllegalStateException(AbstractHashedMap.GETVALUE_INVALID);
            }
            return current.getValue();
        }

        @Override
        public K next() {
            return super.nextEntry().getKey();

public boolean containsKey(final Object key1, final Object key2, final Object key3,
                               final Object key4, final Object key5) {
        final int hashCode = hash(key1, key2, key3, key4, key5);
        AbstractHashedMap.HashEntry<MultiKey<? extends K>, V> entry =
                decorated().data[decorated().hashIndex(hashCode, decorated().data.length)];
        while (entry != null) {
            if (entry.hashCode == hashCode && isEqualKey(entry, key1, key2, key3, key4, key5)) {
                return true;

multi.size() == 4 &&
            (key1 == multi.getKey(0) || key1 != null && key1.equals(multi.getKey(0))) &&
            (key2 == multi.getKey(1) || key2 != null && key2.equals(multi.getKey(1))) &&
            (key3 == multi.getKey(2) || key3 != null && key3.equals(multi.getKey(2))) &&
            (key4 == multi.getKey(3) || key4 != null && key4.equals(multi.getKey(3)));

super((Map<K, V>) map);
    }

    @Override
    public void clear() {
        throw new UnsupportedOperationException();
    }

    @Override
    public Set<Map.Entry<K, V>> entrySet() {
        final Set<Map.Entry<K, V>> set = super.entrySet();
        return UnmodifiableEntrySet.unmodifiableEntrySet(set);
    }

    @Override
    public Set<K> keySet() {
        final Set<K> set = super.keySet();
        return UnmodifiableSet.unmodifiableSet(set);
    }

    @Override
    public MapIterator<K, V> mapIterator() {

public boolean containsKey(final Object key1, final Object key2, final Object key3, final Object key4) {
        final int hashCode = hash(key1, key2, key3, key4);
        AbstractHashedMap.HashEntry<MultiKey<? extends K>, V> entry =
                decorated().data[decorated().hashIndex(hashCode, decorated().data.length)];
        while (entry != null) {
            if (entry.hashCode == hashCode && isEqualKey(entry, key1, key2, key3, key4)) {
                return true;