TreeBidiMap

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.collections.bidimap;

import java.util.AbstractSet;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;

import org.apache.commons.collections.KeyValue;
import org.apache.commons.collections.MapIterator;
import org.apache.commons.collections.OrderedBidiMap;
import org.apache.commons.collections.OrderedIterator;
import org.apache.commons.collections.OrderedMapIterator;
import org.apache.commons.collections.iterators.EmptyOrderedMapIterator;
import org.apache.commons.collections.keyvalue.UnmodifiableMapEntry;

import static org.apache.commons.collections.bidimap.TreeBidiMap.DataElement.KEY;
import static org.apache.commons.collections.bidimap.TreeBidiMap.DataElement.VALUE;

/**
 * Red-Black tree-based implementation of BidiMap where all objects added
 * implement the <code>Comparable</code> interface.
 * <p>
 * This class guarantees that the map will be in both ascending key order
 * and ascending value order, sorted according to the natural order for
 * the key's and value's classes.
 * <p>
 * This Map is intended for applications that need to be able to look
 * up a key-value pairing by either key or value, and need to do so
 * with equal efficiency.
 * <p>
 * While that goal could be accomplished by taking a pair of TreeMaps
 * and redirecting requests to the appropriate TreeMap (e.g.,
 * containsKey would be directed to the TreeMap that maps values to
 * keys, containsValue would be directed to the TreeMap that maps keys
 * to values), there are problems with that implementation.
 * If the data contained in the TreeMaps is large, the cost of redundant
 * storage becomes significant. The {@link DualTreeBidiMap} and
 * {@link DualHashBidiMap} implementations use this approach.
 * <p>
 * This solution keeps minimizes the data storage by holding data only once.
 * The red-black algorithm is based on {@link java.util.TreeMap}, but has been modified
 * to simultaneously map a tree node by key and by value. This doubles the
 * cost of put operations (but so does using two TreeMaps), and nearly doubles
 * the cost of remove operations (there is a savings in that the lookup of the
 * node to be removed only has to be performed once). And since only one node
 * contains the key and value, storage is significantly less than that
 * required by two TreeMaps.
 * <p>
 * The Map.Entry instances returned by the appropriate methods will
 * not allow setValue() and will throw an
 * UnsupportedOperationException on attempts to call that method.
 *
 * @since 3.0 (previously DoubleOrderedMap v2.0)
 * @version $Id: TreeBidiMap.java 1429905 2013-01-07 17:15:14Z ggregory $
 */
public class TreeBidiMap<K extends Comparable<K>, V extends Comparable<V>> implements OrderedBidiMap<K, V> {

    static enum DataElement {
        KEY("key"), VALUE("value");

        private final String description;

        /**
         * Create a new TreeBidiMap.DataElement.
         *
         * @param description  the description for the element
         */
        private DataElement(final String description) {
            this.description = description;
        }

        @Override
        public String toString() {
            return description;
        }
    }

    private Node<K, V>[] rootNode;
    private int nodeCount = 0;
    private int modifications = 0;
    private Set<K> keySet;
    private Set<V> valuesSet;
    private Set<Map.Entry<K, V>> entrySet;
    private Inverse inverse = null;

    //-----------------------------------------------------------------------
    /**
     * Constructs a new empty TreeBidiMap.
     */
    @SuppressWarnings("unchecked")
    public TreeBidiMap() {
        super();
        rootNode = new Node[2];
    }

    /**
     * Constructs a new TreeBidiMap by copying an existing Map.
     *
     * @param map  the map to copy
     * @throws ClassCastException if the keys/values in the map are
     *  not Comparable or are not mutually comparable
     * @throws NullPointerException if any key or value in the map is null
     */
    public TreeBidiMap(final Map<K, V> map) {
        this();
        putAll(map);
    }

    //-----------------------------------------------------------------------
    /**
     * Returns the number of key-value mappings in this map.
     *
     * @return the number of key-value mappings in this map
     */
    public int size() {
        return nodeCount;
    }

    /**
     * Checks whether the map is empty or not.
     *
     * @return true if the map is empty
     */
    public boolean isEmpty() {
        return nodeCount == 0;
    }

    /**
     * Checks whether this map contains the a mapping for the specified key.
     * <p>
     * The key must implement <code>Comparable</code>.
     *
     * @param key  key whose presence in this map is to be tested
     * @return true if this map contains a mapping for the specified key
     * @throws ClassCastException if the key is of an inappropriate type
     * @throws NullPointerException if the key is null
     */
    public boolean containsKey(final Object key) {
        checkKey(key);
        return lookupKey(key) != null;
    }

    /**
     * Checks whether this map contains the a mapping for the specified value.
     * <p>
     * The value must implement <code>Comparable</code>.
     *
     * @param value  value whose presence in this map is to be tested
     * @return true if this map contains a mapping for the specified value
     * @throws ClassCastException if the value is of an inappropriate type
     * @throws NullPointerException if the value is null
     */
    public boolean containsValue(final Object value) {
        checkValue(value);
        return lookupValue(value) != null;
    }

    /**
     * Gets the value to which this map maps the specified key.
     * Returns null if the map contains no mapping for this key.
     * <p>
     * The key must implement <code>Comparable</code>.
     *
     * @param key  key whose associated value is to be returned
     * @return the value to which this map maps the specified key,
     *  or null if the map contains no mapping for this key
     * @throws ClassCastException if the key is of an inappropriate type
     * @throws NullPointerException if the key is null
     */
    public V get(final Object key) {
        checkKey(key);
        final Node<K, V> node = lookupKey(key);
        return node == null ? null : node.getValue();
    }

    /**
     * Puts the key-value pair into the map, replacing any previous pair.
     * <p>
     * When adding a key-value pair, the value may already exist in the map
     * against a different key. That mapping is removed, to ensure that the
     * value only occurs once in the inverse map.
     * <pre>
     *  BidiMap map1 = new TreeBidiMap();
     *  map.put("A","B");  // contains A mapped to B, as per Map
     *  map.put("A","C");  // contains A mapped to C, as per Map
     *
     *  BidiMap map2 = new TreeBidiMap();
     *  map.put("A","B");  // contains A mapped to B, as per Map
     *  map.put("C","B");  // contains C mapped to B, key A is removed
     * </pre>
     * <p>
     * Both key and value must implement <code>Comparable</code>.
     *
     * @param key  key with which the specified value is to be  associated
     * @param value  value to be associated with the specified key
     * @return the previous value for the key
     * @throws ClassCastException if the key is of an inappropriate type
     * @throws NullPointerException if the key is null
     */
    public V put(final K key, final V value) {
        final V result = get(key);
        doPut(key, value);
        return result;
    }

    /**
     * Puts all the mappings from the specified map into this map.
     * <p>
     * All keys and values must implement <code>Comparable</code>.
     *
     * @param map  the map to copy from
     */
    public void putAll(final Map<? extends K, ? extends V> map) {
        for (final Map.Entry<? extends K, ? extends V> e : map.entrySet()) {
            put(e.getKey(), e.getValue());
        }
    }

    /**
     * Removes the mapping for this key from this map if present.
     * <p>
     * The key must implement <code>Comparable</code>.
     *
     * @param key  key whose mapping is to be removed from the map.
     * @return previous value associated with specified key,
     *  or null if there was no mapping for key.
     * @throws ClassCastException if the key is of an inappropriate type
     * @throws NullPointerException if the key is null
     */
    public V remove(final Object key) {
        return doRemoveKey(key);
    }

    /**
     * Removes all mappings from this map.
     */
    public void clear() {
        modify();

        nodeCount = 0;
        rootNode[KEY.ordinal()] = null;
        rootNode[VALUE.ordinal()] = null;
    }

    //-----------------------------------------------------------------------
    /**
     * Returns the key to which this map maps the specified value.
     * Returns null if the map contains no mapping for this value.
     * <p>
     * The value must implement <code>Comparable</code>.
     *
     * @param value  value whose associated key is to be returned.
     * @return the key to which this map maps the specified value,
     *  or null if the map contains no mapping for this value.
     * @throws ClassCastException if the value is of an inappropriate type
     * @throws NullPointerException if the value is null
     */
    public K getKey(final Object value) {
        checkValue(value);
        final Node<K, V> node = lookupValue(value);
        return node == null ? null : node.getKey();
    }

    /**
     * Removes the mapping for this value from this map if present.
     * <p>
     * The value must implement <code>Comparable</code>.
     *
     * @param value  value whose mapping is to be removed from the map
     * @return previous key associated with specified value,
     *  or null if there was no mapping for value.
     * @throws ClassCastException if the value is of an inappropriate type
     * @throws NullPointerException if the value is null
     */
    public K removeValue(final Object value) {
        return doRemoveValue(value);
    }

    //-----------------------------------------------------------------------
    /**
     * Gets the first (lowest) key currently in this map.
     *
     * @return the first (lowest) key currently in this sorted map
     * @throws NoSuchElementException if this map is empty
     */
    public K firstKey() {
        if (nodeCount == 0) {
            throw new NoSuchElementException("Map is empty");
        }
        return leastNode(rootNode[KEY.ordinal()], KEY).getKey();
    }

    /**
     * Gets the last (highest) key currently in this map.
     *
     * @return the last (highest) key currently in this sorted map
     * @throws NoSuchElementException if this map is empty
     */
    public K lastKey() {
        if (nodeCount == 0) {
            throw new NoSuchElementException("Map is empty");
        }
        return greatestNode(rootNode[KEY.ordinal()], KEY).getKey();
    }

    /**
     * Gets the next key after the one specified.
     * <p>
     * The key must implement <code>Comparable</code>.
     *
     * @param key the key to search for next from
     * @return the next key, null if no match or at end
     */
    public K nextKey(final K key) {
        checkKey(key);
        final Node<K, V> node = nextGreater(lookupKey(key), KEY);
        return node == null ? null : node.getKey();
    }

    /**
     * Gets the previous key before the one specified.
     * <p>
     * The key must implement <code>Comparable</code>.
     *
     * @param key the key to search for previous from
     * @return the previous key, null if no match or at start
     */
    public K previousKey(final K key) {
        checkKey(key);
        final Node<K, V> node = nextSmaller(lookupKey(key), KEY);
        return node == null ? null : node.getKey();
    }

    //-----------------------------------------------------------------------
    /**
     * Returns a set view of the keys contained in this map in key order.
     * <p>
     * The set is backed by the map, so changes to the map are reflected in
     * the set, and vice-versa. If the map is modified while an iteration over
     * the set is in progress, the results of the iteration are undefined.
     * <p>
     * The set supports element removal, which removes the corresponding mapping
     * from the map. It does not support the add or addAll operations.
     *
     * @return a set view of the keys contained in this map.
     */
    public Set<K> keySet() {
        if (keySet == null) {
            keySet = new KeyView(KEY);
        }
        return keySet;
    }

    //-----------------------------------------------------------------------
    /**
     * Returns a set view of the values contained in this map in key order.
     * The returned object can be cast to a Set.
     * <p>
     * The set is backed by the map, so changes to the map are reflected in
     * the set, and vice-versa. If the map is modified while an iteration over
     * the set is in progress, the results of the iteration are undefined.
     * <p>
     * The set supports element removal, which removes the corresponding mapping
     * from the map. It does not support the add or addAll operations.
     *
     * @return a set view of the values contained in this map.
     */
    public Collection<V> values() {
        if (valuesSet == null) {
            valuesSet = new ValueView(KEY);
        }
        return valuesSet;
    }

    //-----------------------------------------------------------------------
    /**
     * Returns a set view of the entries contained in this map in key order.
     * For simple iteration through the map, the MapIterator is quicker.
     * <p>
     * The set is backed by the map, so changes to the map are reflected in
     * the set, and vice-versa. If the map is modified while an iteration over
     * the set is in progress, the results of the iteration are undefined.
     * <p>
     * The set supports element removal, which removes the corresponding mapping
     * from the map. It does not support the add or addAll operations.
     * The returned MapEntry objects do not support setValue.
     *
     * @return a set view of the values contained in this map.
     */
    public Set<Map.Entry<K, V>> entrySet() {
        if (entrySet == null) {
            entrySet = new EntryView();
        }
        return entrySet;
    }

    //-----------------------------------------------------------------------
    public OrderedMapIterator<K, V> mapIterator() {
        if (isEmpty()) {
            return EmptyOrderedMapIterator.<K, V>emptyOrderedMapIterator();
        }
        return new ViewMapIterator(KEY);
    }

    //-----------------------------------------------------------------------
    /**
     * Gets the inverse map for comparison.
     *
     * @return the inverse map
     */
    public OrderedBidiMap<V, K> inverseBidiMap() {
        if (inverse == null) {
            inverse = new Inverse();
        }
        return inverse;
    }

    //-----------------------------------------------------------------------
    /**
     * Compares for equals as per the API.
     *
     * @param obj  the object to compare to
     * @return true if equal
     */
    @Override
    public boolean equals(final Object obj) {
        return this.doEquals(obj, KEY);
    }

    /**
     * Gets the hash code value for this map as per the API.
     *
     * @return the hash code value for this map
     */
    @Override
    public int hashCode() {
        return this.doHashCode(KEY);
    }

    /**
     * Returns a string version of this Map in standard format.
     *
     * @return a standard format string version of the map
     */
    @Override
    public String toString() {
        return this.doToString(KEY);
    }

    //-----------------------------------------------------------------------
    /**
     * Put logic.
     *
     * @param key  the key, always the main map key
     * @param value  the value, always the main map value
     */
    private void doPut(final K key, final V value) {
        checkKeyAndValue(key, value);

        // store previous and remove previous mappings
        doRemoveKey(key);
        doRemoveValue(value);

        Node<K, V> node = rootNode[KEY.ordinal()];
        if (node == null) {
            // map is empty
            final Node<K, V> root = new Node<K, V>(key, value);
            rootNode[KEY.ordinal()] = root;
            rootNode[VALUE.ordinal()] = root;
            grow();

        } else {
            // add new mapping
            while (true) {
                final int cmp = compare(key, node.getKey());

                if (cmp == 0) {
                    // shouldn't happen
                    throw new IllegalArgumentException("Cannot store a duplicate key (\"" + key + "\") in this Map");
                } else if (cmp < 0) {
                    if (node.getLeft(KEY) != null) {
                        node = node.getLeft(KEY);
                    } else {
                        final Node<K, V> newNode = new Node<K, V>(key, value);

                        insertValue(newNode);
                        node.setLeft(newNode, KEY);
                        newNode.setParent(node, KEY);
                        doRedBlackInsert(newNode, KEY);
                        grow();

                        break;
                    }
                } else { // cmp > 0
                    if (node.getRight(KEY) != null) {
                        node = node.getRight(KEY);
                    } else {
                        final Node<K, V> newNode = new Node<K, V>(key, value);

                        insertValue(newNode);
                        node.setRight(newNode, KEY);
                        newNode.setParent(node, KEY);
                        doRedBlackInsert(newNode, KEY);
                        grow();

                        break;
                    }
                }
            }
        }
    }

    private V doRemoveKey(final Object key) {
        final Node<K, V> node = lookupKey(key);
        if (node == null) {
            return null;
        }
        doRedBlackDelete(node);
        return node.getValue();
    }

    private K doRemoveValue(final Object value) {
        final Node<K, V> node = lookupValue(value);
        if (node == null) {
            return null;
        }
        doRedBlackDelete(node);
        return node.getKey();
    }

    /**
     * do the actual lookup of a piece of data
     *
     * @param data the key or value to be looked up
     * @param index  the KEY or VALUE int
     * @return the desired Node, or null if there is no mapping of the
     *         specified data
     */
    @SuppressWarnings("unchecked")
    private <T extends Comparable<T>> Node<K, V> lookup(final Object data, final DataElement dataElement) {
        Node<K, V> rval = null;
        Node<K, V> node = rootNode[dataElement.ordinal()];

        while (node != null) {
            final int cmp = compare((T) data, (T) node.getData(dataElement));
            if (cmp == 0) {
                rval = node;
                break;
            } else {
                node = cmp < 0 ? node.getLeft(dataElement) : node.getRight(dataElement);
            }
        }

        return rval;
    }

    private Node<K, V> lookupKey(final Object key) {
        return this.<K>lookup(key, KEY);
    }

    private Node<K, V> lookupValue(final Object value) {
        return this.<V>lookup(value, VALUE);
    }

    /**
     * get the next larger node from the specified node
     *
     * @param node the node to be searched from
     * @param index  the KEY or VALUE int
     * @return the specified node
     */
    private Node<K, V> nextGreater(final Node<K, V> node, final DataElement dataElement) {
        Node<K, V> rval;
        if (node == null) {
            rval = null;
        } else if (node.getRight(dataElement) != null) {
            // everything to the node's right is larger. The least of
            // the right node's descendants is the next larger node
            rval = leastNode(node.getRight(dataElement), dataElement);
        } else {
            // traverse up our ancestry until we find an ancestor that
            // is null or one whose left child is our ancestor. If we
            // find a null, then this node IS the largest node in the
            // tree, and there is no greater node. Otherwise, we are
            // the largest node in the subtree on that ancestor's left
            // ... and that ancestor is the next greatest node
            Node<K, V> parent = node.getParent(dataElement);
            Node<K, V> child = node;

            while (parent != null && child == parent.getRight(dataElement)) {
                child = parent;
                parent = parent.getParent(dataElement);
            }
            rval = parent;
        }
        return rval;
    }

    /**
     * get the next larger node from the specified node
     *
     * @param node the node to be searched from
     * @param index  the KEY or VALUE int
     * @return the specified node
     */
    private Node<K, V> nextSmaller(final Node<K, V> node, final DataElement dataElement) {
        Node<K, V> rval;
        if (node == null) {
            rval = null;
        } else if (node.getLeft(dataElement) != null) {
            // everything to the node's left is smaller. The greatest of
            // the left node's descendants is the next smaller node
            rval = greatestNode(node.getLeft(dataElement), dataElement);
        } else {
            // traverse up our ancestry until we find an ancestor that
            // is null or one whose right child is our ancestor. If we
            // find a null, then this node IS the largest node in the
            // tree, and there is no greater node. Otherwise, we are
            // the largest node in the subtree on that ancestor's right
            // ... and that ancestor is the next greatest node
            Node<K, V> parent = node.getParent(dataElement);
            Node<K, V> child = node;

            while (parent != null && child == parent.getLeft(dataElement)) {
                child = parent;
                parent = parent.getParent(dataElement);
            }
            rval = parent;
        }
        return rval;
    }

    //-----------------------------------------------------------------------

    /**
     * Compare two objects
     *
     * @param o1  the first object
     * @param o2  the second object
     *
     * @return negative value if o1 &lt; o2; 0 if o1 == o2; positive
     *         value if o1 &gt; o2
     */
    private static <T extends Comparable<T>> int compare(final T o1, final T o2) {
        return o1.compareTo(o2);
    }

    /**
     * Find the least node from a given node.
     *
     * @param node  the node from which we will start searching
     * @param index  the KEY or VALUE int
     * @return the smallest node, from the specified node, in the
     *         specified mapping
     */
    private Node<K, V> leastNode(final Node<K, V> node, final DataElement dataElement) {
        Node<K, V> rval = node;
        if (rval != null) {
            while (rval.getLeft(dataElement) != null) {
                rval = rval.getLeft(dataElement);
            }
        }
        return rval;
    }

    /**
     * Find the greatest node from a given node.
     *
     * @param node  the node from which we will start searching
     * @param index  the KEY or VALUE int
     * @return the greatest node, from the specified node
     */
    private Node<K, V> greatestNode(final Node<K, V> node, final DataElement dataElement) {
        Node<K, V> rval = node;
        if (rval != null) {
            while (rval.getRight(dataElement) != null) {
                rval = rval.getRight(dataElement);
            }
        }
        return rval;
    }

    /**
     * copy the color from one node to another, dealing with the fact
     * that one or both nodes may, in fact, be null
     *
     * @param from the node whose color we're copying; may be null
     * @param to the node whose color we're changing; may be null
     * @param index  the KEY or VALUE int
     */
    private void copyColor(final Node<K, V> from, final Node<K, V> to, final DataElement dataElement) {
        if (to != null) {
            if (from == null) {
                // by default, make it black
                to.setBlack(dataElement);
            } else {
                to.copyColor(from, dataElement);
            }
        }
    }

    /**
     * is the specified node red? if the node does not exist, no, it's
     * black, thank you
     *
     * @param node the node (may be null) in question
     * @param index  the KEY or VALUE int
     */
    private static boolean isRed(final Node<?, ?> node, final DataElement dataElement) {
        return node != null && node.isRed(dataElement);
    }

    /**
     * is the specified black red? if the node does not exist, sure,
     * it's black, thank you
     *
     * @param node the node (may be null) in question
     * @param index  the KEY or VALUE int
     */
    private static boolean isBlack(final Node<?, ?> node, final DataElement dataElement) {
        return node == null || node.isBlack(dataElement);
    }

    /**
     * force a node (if it exists) red
     *
     * @param node the node (may be null) in question
     * @param index  the KEY or VALUE int
     */
    private static void makeRed(final Node<?, ?> node, final DataElement dataElement) {
        if (node != null) {
            node.setRed(dataElement);
        }
    }

    /**
     * force a node (if it exists) black
     *
     * @param node the node (may be null) in question
     * @param index  the KEY or VALUE int
     */
    private static void makeBlack(final Node<?, ?> node, final DataElement dataElement) {
        if (node != null) {
            node.setBlack(dataElement);
        }
    }

    /**
     * get a node's grandparent. mind you, the node, its parent, or
     * its grandparent may not exist. no problem
     *
     * @param node the node (may be null) in question
     * @param index  the KEY or VALUE int
     */
    private Node<K, V> getGrandParent(final Node<K, V> node, final DataElement dataElement) {
        return getParent(getParent(node, dataElement), dataElement);
    }

    /**
     * get a node's parent. mind you, the node, or its parent, may not
     * exist. no problem
     *
     * @param node the node (may be null) in question
     * @param index  the KEY or VALUE int
     */
    private Node<K, V> getParent(final Node<K, V> node, final DataElement dataElement) {
        return node == null ? null : node.getParent(dataElement);
    }

    /**
     * get a node's right child. mind you, the node may not exist. no
     * problem
     *
     * @param node the node (may be null) in question
     * @param index  the KEY or VALUE int
     */
    private Node<K, V> getRightChild(final Node<K, V> node, final DataElement dataElement) {
        return node == null ? null : node.getRight(dataElement);
    }

    /**
     * get a node's left child. mind you, the node may not exist. no
     * problem
     *
     * @param node the node (may be null) in question
     * @param index  the KEY or VALUE int
     */
    private Node<K, V> getLeftChild(final Node<K, V> node, final DataElement dataElement) {
        return node == null ? null : node.getLeft(dataElement);
    }

    /**
     * do a rotate left. standard fare in the world of balanced trees
     *
     * @param node the node to be rotated
     * @param index  the KEY or VALUE int
     */
    private void rotateLeft(final Node<K, V> node, final DataElement dataElement) {
        final Node<K, V> rightChild = node.getRight(dataElement);
        node.setRight(rightChild.getLeft(dataElement), dataElement);

        if (rightChild.getLeft(dataElement) != null) {
            rightChild.getLeft(dataElement).setParent(node, dataElement);
        }
        rightChild.setParent(node.getParent(dataElement), dataElement);

        if (node.getParent(dataElement) == null) {
            // node was the root ... now its right child is the root
            rootNode[dataElement.ordinal()] = rightChild;
        } else if (node.getParent(dataElement).getLeft(dataElement) == node) {
            node.getParent(dataElement).setLeft(rightChild, dataElement);
        } else {
            node.getParent(dataElement).setRight(rightChild, dataElement);
        }

        rightChild.setLeft(node, dataElement);
        node.setParent(rightChild, dataElement);
    }

    /**
     * do a rotate right. standard fare in the world of balanced trees
     *
     * @param node the node to be rotated
     * @param index  the KEY or VALUE int
     */
    private void rotateRight(final Node<K, V> node, final DataElement dataElement) {
        final Node<K, V> leftChild = node.getLeft(dataElement);
        node.setLeft(leftChild.getRight(dataElement), dataElement);
        if (leftChild.getRight(dataElement) != null) {
            leftChild.getRight(dataElement).setParent(node, dataElement);
        }
        leftChild.setParent(node.getParent(dataElement), dataElement);

        if (node.getParent(dataElement) == null) {
            // node was the root ... now its left child is the root
            rootNode[dataElement.ordinal()] = leftChild;
        } else if (node.getParent(dataElement).getRight(dataElement) == node) {
            node.getParent(dataElement).setRight(leftChild, dataElement);
        } else {
            node.getParent(dataElement).setLeft(leftChild, dataElement);
        }

        leftChild.setRight(node, dataElement);
        node.setParent(leftChild, dataElement);
    }

    /**
     * complicated red-black insert stuff. Based on Sun's TreeMap
     * implementation, though it's barely recognizable any more
     *
     * @param insertedNode the node to be inserted
     * @param dataElement  the KEY or VALUE int
     */
    private void doRedBlackInsert(final Node<K, V> insertedNode, final DataElement dataElement) {
        Node<K, V> currentNode = insertedNode;
        makeRed(currentNode, dataElement);

        while (currentNode != null
            && currentNode != rootNode[dataElement.ordinal()]
            && isRed(currentNode.getParent(dataElement), dataElement)) {
            if (currentNode.isLeftChild(dataElement)) {
                final Node<K, V> y = getRightChild(getGrandParent(currentNode, dataElement), dataElement);

                if (isRed(y, dataElement)) {
                    makeBlack(getParent(currentNode, dataElement), dataElement);
                    makeBlack(y, dataElement);
                    makeRed(getGrandParent(currentNode, dataElement), dataElement);

                    currentNode = getGrandParent(currentNode, dataElement);
                } else {
                    //dead code?
                    if (currentNode.isRightChild(dataElement)) {
                        currentNode = getParent(currentNode, dataElement);

                        rotateLeft(currentNode, dataElement);
                    }

                    makeBlack(getParent(currentNode, dataElement), dataElement);
                    makeRed(getGrandParent(currentNode, dataElement), dataElement);

                    if (getGrandParent(currentNode, dataElement) != null) {
                        rotateRight(getGrandParent(currentNode, dataElement), dataElement);
                    }
                }
            } else {

                // just like clause above, except swap left for right
                final Node<K, V> y = getLeftChild(getGrandParent(currentNode, dataElement), dataElement);

                if (isRed(y, dataElement)) {
                    makeBlack(getParent(currentNode, dataElement), dataElement);
                    makeBlack(y, dataElement);
                    makeRed(getGrandParent(currentNode, dataElement), dataElement);

                    currentNode = getGrandParent(currentNode, dataElement);
                } else {
                    //dead code?
                    if (currentNode.isLeftChild(dataElement)) {
                        currentNode = getParent(currentNode, dataElement);

                        rotateRight(currentNode, dataElement);
                    }

                    makeBlack(getParent(currentNode, dataElement), dataElement);
                    makeRed(getGrandParent(currentNode, dataElement), dataElement);

                    if (getGrandParent(currentNode, dataElement) != null) {
                        rotateLeft(getGrandParent(currentNode, dataElement), dataElement);
                    }
                }
            }
        }

        makeBlack(rootNode[dataElement.ordinal()], dataElement);
    }

    /**
     * complicated red-black delete stuff. Based on Sun's TreeMap
     * implementation, though it's barely recognizable any more
     *
     * @param deletedNode the node to be deleted
     */
    private void doRedBlackDelete(final Node<K, V> deletedNode) {
        for (final DataElement dataElement : DataElement.values()) {
            // if deleted node has both left and children, swap with
            // the next greater node
            if (deletedNode.getLeft(dataElement) != null && deletedNode.getRight(dataElement) != null) {
                swapPosition(nextGreater(deletedNode, dataElement), deletedNode, dataElement);
            }

            final Node<K, V> replacement = deletedNode.getLeft(dataElement) != null ?
                    deletedNode.getLeft(dataElement) : deletedNode.getRight(dataElement);

            if (replacement != null) {
                replacement.setParent(deletedNode.getParent(dataElement), dataElement);

                if (deletedNode.getParent(dataElement) == null) {
                    rootNode[dataElement.ordinal()] = replacement;
                } else if (deletedNode == deletedNode.getParent(dataElement).getLeft(dataElement)) {
                    deletedNode.getParent(dataElement).setLeft(replacement, dataElement);
                } else {
                    deletedNode.getParent(dataElement).setRight(replacement, dataElement);
                }

                deletedNode.setLeft(null, dataElement);
                deletedNode.setRight(null, dataElement);
                deletedNode.setParent(null, dataElement);

                if (isBlack(deletedNode, dataElement)) {
                    doRedBlackDeleteFixup(replacement, dataElement);
                }
            } else {

                // replacement is null
                if (deletedNode.getParent(dataElement) == null) {

                    // empty tree
                    rootNode[dataElement.ordinal()] = null;
                } else {

                    // deleted node had no children
                    if (isBlack(deletedNode, dataElement)) {
                        doRedBlackDeleteFixup(deletedNode, dataElement);
                    }

                    if (deletedNode.getParent(dataElement) != null) {
                        if (deletedNode == deletedNode.getParent(dataElement).getLeft(dataElement)) {
                            deletedNode.getParent(dataElement).setLeft(null, dataElement);
                        } else {
                            deletedNode.getParent(dataElement).setRight(null, dataElement);
                        }

                        deletedNode.setParent(null, dataElement);
                    }
                }
            }
        }
        shrink();
    }

     /**
      * complicated red-black delete stuff. Based on Sun's TreeMap
      * implementation, though it's barely recognizable any more. This
      * rebalances the tree (somewhat, as red-black trees are not
      * perfectly balanced -- perfect balancing takes longer)
      *
      * @param replacementNode the node being replaced
      * @param dataElement  the KEY or VALUE int
      */
     private void doRedBlackDeleteFixup(final Node<K, V> replacementNode, final DataElement dataElement) {
         Node<K, V> currentNode = replacementNode;

         while (currentNode != rootNode[dataElement.ordinal()] && isBlack(currentNode, dataElement)) {
             if (currentNode.isLeftChild(dataElement)) {
                 Node<K, V> siblingNode = getRightChild(getParent(currentNode, dataElement), dataElement);

                 if (isRed(siblingNode, dataElement)) {
                     makeBlack(siblingNode, dataElement);
                     makeRed(getParent(currentNode, dataElement), dataElement);
                     rotateLeft(getParent(currentNode, dataElement), dataElement);

                     siblingNode = getRightChild(getParent(currentNode, dataElement), dataElement);
                 }

                 if (isBlack(getLeftChild(siblingNode, dataElement), dataElement)
                     && isBlack(getRightChild(siblingNode, dataElement), dataElement)) {
                     makeRed(siblingNode, dataElement);

                     currentNode = getParent(currentNode, dataElement);
                 } else {
                     if (isBlack(getRightChild(siblingNode, dataElement), dataElement)) {
                         makeBlack(getLeftChild(siblingNode, dataElement), dataElement);
                         makeRed(siblingNode, dataElement);
                         rotateRight(siblingNode, dataElement);

                         siblingNode = getRightChild(getParent(currentNode, dataElement), dataElement);
                     }

                     copyColor(getParent(currentNode, dataElement), siblingNode, dataElement);
                     makeBlack(getParent(currentNode, dataElement), dataElement);
                     makeBlack(getRightChild(siblingNode, dataElement), dataElement);
                     rotateLeft(getParent(currentNode, dataElement), dataElement);

                     currentNode = rootNode[dataElement.ordinal()];
                 }
             } else {
                 Node<K, V> siblingNode = getLeftChild(getParent(currentNode, dataElement), dataElement);

                 if (isRed(siblingNode, dataElement)) {
                     makeBlack(siblingNode, dataElement);
                     makeRed(getParent(currentNode, dataElement), dataElement);
                     rotateRight(getParent(currentNode, dataElement), dataElement);

                     siblingNode = getLeftChild(getParent(currentNode, dataElement), dataElement);
                 }

                 if (isBlack(getRightChild(siblingNode, dataElement), dataElement)
                     && isBlack(getLeftChild(siblingNode, dataElement), dataElement)) {
                     makeRed(siblingNode, dataElement);

                     currentNode = getParent(currentNode, dataElement);
                 } else {
                     if (isBlack(getLeftChild(siblingNode, dataElement), dataElement)) {
                         makeBlack(getRightChild(siblingNode, dataElement), dataElement);
                         makeRed(siblingNode, dataElement);
                         rotateLeft(siblingNode, dataElement);

                         siblingNode = getLeftChild(getParent(currentNode, dataElement), dataElement);
                     }

                     copyColor(getParent(currentNode, dataElement), siblingNode, dataElement);
                     makeBlack(getParent(currentNode, dataElement), dataElement);
                     makeBlack(getLeftChild(siblingNode, dataElement), dataElement);
                     rotateRight(getParent(currentNode, dataElement), dataElement);

                     currentNode = rootNode[dataElement.ordinal()];
                 }
             }
         }

         makeBlack(currentNode, dataElement);
     }

     /**
      * swap two nodes (except for their content), taking care of
      * special cases where one is the other's parent ... hey, it
      * happens.
      *
      * @param x one node
      * @param y another node
      * @param dataElement  the KEY or VALUE int
      */
     private void swapPosition(final Node<K, V> x, final Node<K, V> y, final DataElement dataElement) {
         // Save initial values.
         final Node<K, V> xFormerParent = x.getParent(dataElement);
         final Node<K, V> xFormerLeftChild = x.getLeft(dataElement);
         final Node<K, V> xFormerRightChild = x.getRight(dataElement);
         final Node<K, V> yFormerParent = y.getParent(dataElement);
         final Node<K, V> yFormerLeftChild = y.getLeft(dataElement);
         final Node<K, V> yFormerRightChild = y.getRight(dataElement);
         final boolean xWasLeftChild =
                 x.getParent(dataElement) != null && x == x.getParent(dataElement).getLeft(dataElement);
         final boolean yWasLeftChild =
                 y.getParent(dataElement) != null && y == y.getParent(dataElement).getLeft(dataElement);

         // Swap, handling special cases of one being the other's parent.
         if (x == yFormerParent) { // x was y's parent
             x.setParent(y, dataElement);

             if (yWasLeftChild) {
                 y.setLeft(x, dataElement);
                 y.setRight(xFormerRightChild, dataElement);
             } else {
                 y.setRight(x, dataElement);
                 y.setLeft(xFormerLeftChild, dataElement);
             }
         } else {
             x.setParent(yFormerParent, dataElement);

             if (yFormerParent != null) {
                 if (yWasLeftChild) {
                     yFormerParent.setLeft(x, dataElement);
                 } else {
                     yFormerParent.setRight(x, dataElement);
                 }
             }

             y.setLeft(xFormerLeftChild, dataElement);
             y.setRight(xFormerRightChild, dataElement);
         }

         if (y == xFormerParent) { // y was x's parent
             y.setParent(x, dataElement);

             if (xWasLeftChild) {
                 x.setLeft(y, dataElement);
                 x.setRight(yFormerRightChild, dataElement);
             } else {
                 x.setRight(y, dataElement);
                 x.setLeft(yFormerLeftChild, dataElement);
             }
         } else {
             y.setParent(xFormerParent, dataElement);

             if (xFormerParent != null) {
                 if (xWasLeftChild) {
                     xFormerParent.setLeft(y, dataElement);
                 } else {
                     xFormerParent.setRight(y, dataElement);
                 }
             }

             x.setLeft(yFormerLeftChild, dataElement);
             x.setRight(yFormerRightChild, dataElement);
         }

         // Fix children's parent pointers
         if (x.getLeft(dataElement) != null) {
             x.getLeft(dataElement).setParent(x, dataElement);
         }

         if (x.getRight(dataElement) != null) {
             x.getRight(dataElement).setParent(x, dataElement);
         }

         if (y.getLeft(dataElement) != null) {
             y.getLeft(dataElement).setParent(y, dataElement);
         }

         if (y.getRight(dataElement) != null) {
             y.getRight(dataElement).setParent(y, dataElement);
         }

         x.swapColors(y, dataElement);

         // Check if root changed
         if (rootNode[dataElement.ordinal()] == x) {
             rootNode[dataElement.ordinal()] = y;
         } else if (rootNode[dataElement.ordinal()] == y) {
             rootNode[dataElement.ordinal()] = x;
         }
     }

     /**
      * check if an object is fit to be proper input ... has to be
      * Comparable and non-null
      *
      * @param o the object being checked
      * @param index  the KEY or VALUE int (used to put the right word in the
      *              exception message)
      *
      * @throws NullPointerException if o is null
      * @throws ClassCastException if o is not Comparable
      */
     private static void checkNonNullComparable(final Object o, final DataElement dataElement) {
         if (o == null) {
             throw new NullPointerException(dataElement + " cannot be null");
         }
         if (!(o instanceof Comparable)) {
             throw new ClassCastException(dataElement + " must be Comparable");
         }
     }

     /**
      * check a key for validity (non-null and implements Comparable)
      *
      * @param key the key to be checked
      *
      * @throws NullPointerException if key is null
      * @throws ClassCastException if key is not Comparable
      */
     private static void checkKey(final Object key) {
         checkNonNullComparable(key, KEY);
     }

     /**
      * check a value for validity (non-null and implements Comparable)
      *
      * @param value the value to be checked
      *
      * @throws NullPointerException if value is null
      * @throws ClassCastException if value is not Comparable
      */
     private static void checkValue(final Object value) {
         checkNonNullComparable(value, VALUE);
     }

     /**
      * check a key and a value for validity (non-null and implements
      * Comparable)
      *
      * @param key the key to be checked
      * @param value the value to be checked
      *
      * @throws NullPointerException if key or value is null
      * @throws ClassCastException if key or value is not Comparable
      */
     private static void checkKeyAndValue(final Object key, final Object value) {
         checkKey(key);
         checkValue(value);
     }

     /**
      * increment the modification count -- used to check for
      * concurrent modification of the map through the map and through
      * an Iterator from one of its Set or Collection views
      */
     private void modify() {
         modifications++;
     }

     /**
      * bump up the size and note that the map has changed
      */
     private void grow() {
         modify();
         nodeCount++;
     }

     /**
      * decrement the size and note that the map has changed
      */
     private void shrink() {
         modify();
         nodeCount--;
     }

     /**
      * insert a node by its value
      *
      * @param newNode the node to be inserted
      *
      * @throws IllegalArgumentException if the node already exists
      *                                     in the value mapping
      */
     private void insertValue(final Node<K, V> newNode) throws IllegalArgumentException {
         Node<K, V> node = rootNode[VALUE.ordinal()];

         while (true) {
             final int cmp = compare(newNode.getValue(), node.getValue());

             if (cmp == 0) {
                 throw new IllegalArgumentException(
                     "Cannot store a duplicate value (\"" + newNode.getData(VALUE) + "\") in this Map");
             } else if (cmp < 0) {
                 if (node.getLeft(VALUE) != null) {
                     node = node.getLeft(VALUE);
                 } else {
                     node.setLeft(newNode, VALUE);
                     newNode.setParent(node, VALUE);
                     doRedBlackInsert(newNode, VALUE);

                     break;
                 }
             } else { // cmp > 0
                 if (node.getRight(VALUE) != null) {
                     node = node.getRight(VALUE);
                 } else {
                     node.setRight(newNode, VALUE);
                     newNode.setParent(node, VALUE);
                     doRedBlackInsert(newNode, VALUE);

                     break;
                 }
             }
         }
     }

     //-----------------------------------------------------------------------
     /**
      * Compares for equals as per the API.
      *
      * @param obj  the object to compare to
      * @param type  the KEY or VALUE int
      * @return true if equal
      */
     private boolean doEquals(final Object obj, final DataElement dataElement) {
         if (obj == this) {
             return true;
         }
         if (obj instanceof Map == false) {
             return false;
         }
         final Map<?, ?> other = (Map<?, ?>) obj;
         if (other.size() != size()) {
             return false;
         }

         if (nodeCount > 0) {
             try {
                 for (final MapIterator<?, ?> it = getMapIterator(dataElement); it.hasNext(); ) {
                     final Object key = it.next();
                     final Object value = it.getValue();
                     if (value.equals(other.get(key)) == false) {
                         return false;
                     }
                 }
             } catch (final ClassCastException ex) {
                 return false;
             } catch (final NullPointerException ex) {
                 return false;
             }
         }
         return true;
     }

     /**
      * Gets the hash code value for this map as per the API.
      *
      * @param type  the KEY or VALUE int
      * @return the hash code value for this map
      */
     private int doHashCode(final DataElement dataElement) {
         int total = 0;
         if (nodeCount > 0) {
             for (final MapIterator<?, ?> it = getMapIterator(dataElement); it.hasNext(); ) {
                 final Object key = it.next();
                 final Object value = it.getValue();
                 total += key.hashCode() ^ value.hashCode();
             }
         }
         return total;
     }

     /**
      * Gets the string form of this map as per AbstractMap.
      *
      * @param type  the KEY or VALUE int
      * @return the string form of this map
      */
     private String doToString(final DataElement dataElement) {
         if (nodeCount == 0) {
             return "{}";
         }
         final StringBuilder buf = new StringBuilder(nodeCount * 32);
         buf.append('{');
         final MapIterator<?, ?> it = getMapIterator(dataElement);
         boolean hasNext = it.hasNext();
         while (hasNext) {
             final Object key = it.next();
             final Object value = it.getValue();
             buf.append(key == this ? "(this Map)" : key)
                .append('=')
                .append(value == this ? "(this Map)" : value);

             hasNext = it.hasNext();
             if (hasNext) {
                 buf.append(", ");
             }
         }

         buf.append('}');
         return buf.toString();
     }

     private MapIterator<?, ?> getMapIterator(final DataElement dataElement) {
         switch (dataElement) {
         case KEY:
             return new ViewMapIterator(KEY);
         case VALUE:
             return new InverseViewMapIterator(VALUE);
         default:
             throw new IllegalArgumentException();
         }
     }

     //-----------------------------------------------------------------------
     /**
      * A view of this map.
      */
     abstract class View<E> extends AbstractSet<E> {

         /** Whether to return KEY or VALUE order. */
         protected final DataElement orderType;

         /**
          * Constructor.
          * @param orderType  the KEY or VALUE int for the order
          * @param main  the main map
          */
         View(final DataElement orderType) {
             super();
             this.orderType = orderType;
         }

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

         @Override
         public void clear() {
             TreeBidiMap.this.clear();
         }
     }

     class KeyView extends View<K> {

         /**
          * Create a new TreeBidiMap.KeyView.
          */
         public KeyView(final DataElement orderType) {
             super(orderType);
         }

         @Override
         public Iterator<K> iterator() {
             return new ViewMapIterator(orderType);
         }

         @Override
         public boolean contains(final Object obj) {
             checkNonNullComparable(obj, KEY);
             return lookupKey(obj) != null;
         }

         @Override
         public boolean remove(final Object o) {
             return doRemoveKey(o) != null;
         }

     }

     class ValueView extends View<V> {

         /**
          * Create a new TreeBidiMap.ValueView.
          */
         public ValueView(final DataElement orderType) {
             super(orderType);
         }

         @Override
         public Iterator<V> iterator() {
             return new InverseViewMapIterator(orderType);
         }

         @Override
         public boolean contains(final Object obj) {
             checkNonNullComparable(obj, VALUE);
             return lookupValue(obj) != null;
         }

         @Override
         public boolean remove(final Object o) {
             return doRemoveValue(o) != null;
         }

     }

     /**
      * A view of this map.
      */
     class EntryView extends View<Map.Entry<K, V>> {

         EntryView() {
             super(KEY);
         }

         @Override
         public boolean contains(final Object obj) {
             if (obj instanceof Map.Entry == false) {
                 return false;
             }
             final Map.Entry<?, ?> entry = (Map.Entry<?, ?>) obj;
             final Object value = entry.getValue();
             final Node<K, V> node = lookupKey(entry.getKey());
             return node != null && node.getValue().equals(value);
         }

         @Override
         public boolean remove(final Object obj) {
             if (obj instanceof Map.Entry == false) {
                 return false;
             }
             final Map.Entry<?, ?> entry = (Map.Entry<?, ?>) obj;
             final Object value = entry.getValue();
             final Node<K, V> node = lookupKey(entry.getKey());
             if (node != null && node.getValue().equals(value)) {
                 doRedBlackDelete(node);
                 return true;
             }
             return false;
         }

         @Override
         public Iterator<java.util.Map.Entry<K, V>> iterator() {
             return new ViewMapEntryIterator();
         }
     }

     /**
      * A view of this map.
      */
     class InverseEntryView extends View<Map.Entry<V, K>> {

         InverseEntryView() {
             super(VALUE);
         }

         @Override
         public boolean contains(final Object obj) {
             if (obj instanceof Map.Entry == false) {
                 return false;
             }
             final Map.Entry<?, ?> entry = (Map.Entry<?, ?>) obj;
             final Object value = entry.getValue();
             final Node<K, V> node = lookupValue(entry.getKey());
             return node != null && node.getKey().equals(value);
         }

         @Override
         public boolean remove(final Object obj) {
             if (obj instanceof Map.Entry == false) {
                 return false;
             }
             final Map.Entry<?, ?> entry = (Map.Entry<?, ?>) obj;
             final Object value = entry.getValue();
             final Node<K, V> node = lookupValue(entry.getKey());
             if (node != null && node.getKey().equals(value)) {
                 doRedBlackDelete(node);
                 return true;
             }
             return false;
         }

         @Override
         public Iterator<java.util.Map.Entry<V, K>> iterator() {
             return new InverseViewMapEntryIterator();
         }
     }

     //-----------------------------------------------------------------------
     /**
      * An iterator over the map.
      */
     abstract class ViewIterator {

         /** Whether to return KEY or VALUE order. */
         protected final DataElement orderType;
         /** The last node returned by the iterator. */
         protected Node<K, V> lastReturnedNode;
         /** The next node to be returned by the iterator. */
         protected Node<K, V> nextNode;
         /** The previous node in the sequence returned by the iterator. */
         protected Node<K, V> previousNode;
         /** The modification count. */
         private int expectedModifications;

         /**
          * Constructor.
          * @param orderType  the KEY or VALUE int for the order
          * @param main  the main map
          */
         ViewIterator(final DataElement orderType) {
             super();
             this.orderType = orderType;
             expectedModifications = modifications;
             nextNode = leastNode(rootNode[orderType.ordinal()], orderType);
             lastReturnedNode = null;
             previousNode = null;
         }

         public final boolean hasNext() {
             return nextNode != null;
         }

         protected Node<K, V> navigateNext() {
             if (nextNode == null) {
                 throw new NoSuchElementException();
             }
             if (modifications != expectedModifications) {
                 throw new ConcurrentModificationException();
             }
             lastReturnedNode = nextNode;
             previousNode = nextNode;
             nextNode = nextGreater(nextNode, orderType);
             return lastReturnedNode;
         }

         public boolean hasPrevious() {
             return previousNode != null;
         }

         protected Node<K, V> navigatePrevious() {
             if (previousNode == null) {
                 throw new NoSuchElementException();
             }
             if (modifications != expectedModifications) {
                 throw new ConcurrentModificationException();
             }
             nextNode = lastReturnedNode;
             if (nextNode == null) {
                 nextNode = nextGreater(previousNode, orderType);
             }
             lastReturnedNode = previousNode;
             previousNode = nextSmaller(previousNode, orderType);
             return lastReturnedNode;
         }

         public final void remove() {
             if (lastReturnedNode == null) {
                 throw new IllegalStateException();
             }
             if (modifications != expectedModifications) {
                 throw new ConcurrentModificationException();
             }
             doRedBlackDelete(lastReturnedNode);
             expectedModifications++;
             lastReturnedNode = null;
             if (nextNode == null) {
                 previousNode = greatestNode(rootNode[orderType.ordinal()], orderType);
             } else {
                 previousNode = nextSmaller(nextNode, orderType);
             }
         }
     }

     //-----------------------------------------------------------------------
     /**
      * An iterator over the map.
      */
     class ViewMapIterator extends ViewIterator implements OrderedMapIterator<K, V> {

         /**
          * Constructor.
          */
         ViewMapIterator(final DataElement orderType) {
             super(orderType);
         }

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

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

         public V setValue(final V obj) {
             throw new UnsupportedOperationException();
         }

         public K next() {
             return navigateNext().getKey();
         }

         public K previous() {
             return navigatePrevious().getKey();
         }
     }

     /**
      * An iterator over the map.
      */
     class InverseViewMapIterator extends ViewIterator implements OrderedMapIterator<V, K> {

         /**
          * Create a new TreeBidiMap.InverseViewMapIterator.
          */
         public InverseViewMapIterator(final DataElement orderType) {
             super(orderType);
         }

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

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

         public K setValue(final K obj) {
             throw new UnsupportedOperationException();
         }

         public V next() {
             return navigateNext().getValue();
         }

         public V previous() {
             return navigatePrevious().getValue();
         }
     }

     /**
      * An iterator over the map entries.
      */
     class ViewMapEntryIterator extends ViewIterator implements OrderedIterator<Map.Entry<K, V>> {

         /**
          * Constructor.
          */
         ViewMapEntryIterator() {
             super(KEY);
         }

         public Map.Entry<K, V> next() {
             return navigateNext();
         }

         public Map.Entry<K, V> previous() {
             return navigatePrevious();
         }
     }

     /**
      * An iterator over the inverse map entries.
      */
     class InverseViewMapEntryIterator extends ViewIterator implements OrderedIterator<Map.Entry<V, K>> {

         /**
          * Constructor.
          */
         InverseViewMapEntryIterator() {
             super(VALUE);
         }

         public Map.Entry<V, K> next() {
             return createEntry(navigateNext());
         }

         public Map.Entry<V, K> previous() {
             return createEntry(navigatePrevious());
         }

         private Map.Entry<V, K> createEntry(final Node<K, V> node) {
             return new UnmodifiableMapEntry<V, K>(node.getValue(), node.getKey());
         }
     }

     //-----------------------------------------------------------------------
     //-----------------------------------------------------------------------
     /**
      * A node used to store the data.
      */
     static class Node<K extends Comparable<K>, V extends Comparable<V>> implements Map.Entry<K, V>, KeyValue<K, V> {

         private final K key;
         private final V value;
         private final Node<K, V>[] leftNode;
         private final Node<K, V>[] rightNode;
         private final Node<K, V>[] parentNode;
         private final boolean[] blackColor;
         private int hashcodeValue;
         private boolean calculatedHashCode;

         /**
          * Make a new cell with given key and value, and with null
          * links, and black (true) colors.
          *
          * @param key
          * @param value
          */
         @SuppressWarnings("unchecked")
         Node(final K key, final V value) {
             super();
             this.key = key;
             this.value = value;
             leftNode = new Node[2];
             rightNode = new Node[2];
             parentNode = new Node[2];
             blackColor = new boolean[] { true, true };
             calculatedHashCode = false;
         }

         private Object getData(final DataElement dataElement) {
             switch (dataElement) {
             case KEY:
                 return getKey();
             case VALUE:
                 return getValue();
             default:
                 throw new IllegalArgumentException();
             }
         }

         private void setLeft(final Node<K, V> node, final DataElement dataElement) {
             leftNode[dataElement.ordinal()] = node;
         }

         private Node<K, V> getLeft(final DataElement dataElement) {
             return leftNode[dataElement.ordinal()];
         }

         private void setRight(final Node<K, V> node, final DataElement dataElement) {
             rightNode[dataElement.ordinal()] = node;
         }

         private Node<K, V> getRight(final DataElement dataElement) {
             return rightNode[dataElement.ordinal()];
         }

         /**
          * Set this node's parent node.
          *
          * @param node  the new parent node
          * @param index  the KEY or VALUE int
          */
         private void setParent(final Node<K, V> node, final DataElement dataElement) {
             parentNode[dataElement.ordinal()] = node;
         }

         /**
          * Get the parent node.
          *
          * @param index  the KEY or VALUE int
          * @return the parent node, may be null
          */
         private Node<K, V> getParent(final DataElement dataElement) {
             return parentNode[dataElement.ordinal()];
         }

         /**
          * Exchange colors with another node.
          *
          * @param node  the node to swap with
          * @param index  the KEY or VALUE int
          */
         private void swapColors(final Node<K, V> node, final DataElement dataElement) {
             // Swap colors -- old hacker's trick
             blackColor[dataElement.ordinal()]      ^= node.blackColor[dataElement.ordinal()];
             node.blackColor[dataElement.ordinal()] ^= blackColor[dataElement.ordinal()];
             blackColor[dataElement.ordinal()]      ^= node.blackColor[dataElement.ordinal()];
         }

         /**
          * Is this node black?
          *
          * @param index  the KEY or VALUE int
          * @return true if black (which is represented as a true boolean)
          */
         private boolean isBlack(final DataElement dataElement) {
             return blackColor[dataElement.ordinal()];
         }

         /**
          * Is this node red?
          *
          * @param index  the KEY or VALUE int
          * @return true if non-black
          */
         private boolean isRed(final DataElement dataElement) {
             return !blackColor[dataElement.ordinal()];
         }

         /**
          * Make this node black.
          *
          * @param index  the KEY or VALUE int
          */
         private void setBlack(final DataElement dataElement) {
             blackColor[dataElement.ordinal()] = true;
         }

         /**
          * Make this node red.
          *
          * @param index  the KEY or VALUE int
          */
         private void setRed(final DataElement dataElement) {
             blackColor[dataElement.ordinal()] = false;
         }

         /**
          * Make this node the same color as another
          *
          * @param node  the node whose color we're adopting
          * @param index  the KEY or VALUE int
          */
         private void copyColor(final Node<K, V> node, final DataElement dataElement) {
             blackColor[dataElement.ordinal()] = node.blackColor[dataElement.ordinal()];
         }

         private boolean isLeftChild(final DataElement dataElement) {
             return parentNode[dataElement.ordinal()] != null
                     && parentNode[dataElement.ordinal()].leftNode[dataElement.ordinal()] == this;
         }

         private boolean isRightChild(final DataElement dataElement) {
             return parentNode[dataElement.ordinal()] != null
                     && parentNode[dataElement.ordinal()].rightNode[dataElement.ordinal()] == this;
         }

         //-------------------------------------------------------------------
         /**
          * Gets the key.
          *
          * @return the key corresponding to this entry.
          */
         public K getKey() {
             return key;
         }

         /**
          * Gets the value.
          *
          * @return the value corresponding to this entry.
          */
         public V getValue() {
             return value;
         }

         /**
          * Optional operation that is not permitted in this implementation
          *
          * @param ignored
          * @return does not return
          * @throws UnsupportedOperationException always
          */
         public V setValue(final V ignored) throws UnsupportedOperationException {
             throw new UnsupportedOperationException("Map.Entry.setValue is not supported");
         }

         /**
          * Compares the specified object with this entry for equality.
          * Returns true if the given object is also a map entry and
          * the two entries represent the same mapping.
          *
          * @param obj  the object to be compared for equality with this entry.
          * @return true if the specified object is equal to this entry.
          */
         @Override
         public boolean equals(final Object obj) {
             if (obj == this) {
                 return true;
             }
             if (!(obj instanceof Map.Entry)) {
                 return false;
             }
             final Map.Entry<?, ?> e = (Map.Entry<?, ?>) obj;
             return getKey().equals(e.getKey()) && getValue().equals(e.getValue());
         }

         /**
          * @return the hash code value for this map entry.
          */
         @Override
         public int hashCode() {
             if (!calculatedHashCode) {
                 hashcodeValue = getKey().hashCode() ^ getValue().hashCode();
                 calculatedHashCode = true;
             }
             return hashcodeValue;
         }
     }

     //-----------------------------------------------------------------------
     /**
      * The inverse map implementation.
      */
     class Inverse implements OrderedBidiMap<V, K> {

         /** Store the keySet once created. */
         private Set<V> inverseKeySet;
         /** Store the valuesSet once created. */
         private Set<K> inverseValuesSet;
         /** Store the entrySet once created. */
         private Set<Map.Entry<V, K>> inverseEntrySet;

         public int size() {
             return TreeBidiMap.this.size();
         }

         public boolean isEmpty() {
             return TreeBidiMap.this.isEmpty();
         }

         public K get(final Object key) {
             return TreeBidiMap.this.getKey(key);
         }

         public V getKey(final Object value) {
             return TreeBidiMap.this.get(value);
         }

         public boolean containsKey(final Object key) {
             return TreeBidiMap.this.containsValue(key);
         }

         public boolean containsValue(final Object value) {
             return TreeBidiMap.this.containsKey(value);
         }

         public V firstKey() {
             if (TreeBidiMap.this.nodeCount == 0) {
                 throw new NoSuchElementException("Map is empty");
             }
             return leastNode(TreeBidiMap.this.rootNode[VALUE.ordinal()], VALUE).getValue();
         }

         public V lastKey() {
             if (TreeBidiMap.this.nodeCount == 0) {
                 throw new NoSuchElementException("Map is empty");
             }
             return greatestNode(TreeBidiMap.this.rootNode[VALUE.ordinal()], VALUE).getValue();
         }

         public V nextKey(final V key) {
             checkKey(key);
             final Node<K, V> node = nextGreater(TreeBidiMap.this.<V>lookup(key, VALUE), VALUE);
             return node == null ? null : node.getValue();
         }

         public V previousKey(final V key) {
             checkKey(key);
             final Node<K, V> node = TreeBidiMap.this.nextSmaller(TreeBidiMap.this.<V>lookup(key, VALUE), VALUE);
             return node == null ? null : node.getValue();
         }

         public K put(final V key, final K value) {
             final K result = get(key);
             TreeBidiMap.this.doPut(value, key);
             return result;
         }

         public void putAll(final Map<? extends V, ? extends K> map) {
             for (final Map.Entry<? extends V, ? extends K> e : map.entrySet()) {
                 put(e.getKey(), e.getValue());
             }
         }

         public K remove(final Object key) {
             return TreeBidiMap.this.removeValue(key);
         }

         public V removeValue(final Object value) {
             return TreeBidiMap.this.remove(value);
         }

         public void clear() {
             TreeBidiMap.this.clear();
         }

         public Set<V> keySet() {
             if (inverseKeySet == null) {
                 inverseKeySet = new ValueView(VALUE);
             }
             return inverseKeySet;
         }

         public Collection<K> values() {
             if (inverseValuesSet == null) {
                 inverseValuesSet = new KeyView(VALUE);
             }
             return inverseValuesSet;
         }

         public Set<Map.Entry<V, K>> entrySet() {
             if (inverseEntrySet == null) {
                 inverseEntrySet = new InverseEntryView();
             }
             return inverseEntrySet;
         }

         public OrderedMapIterator<V, K> mapIterator() {
             if (isEmpty()) {
                 return EmptyOrderedMapIterator.<V, K>emptyOrderedMapIterator();
             }
             return new InverseViewMapIterator(VALUE);
         }

         public OrderedBidiMap<K, V> inverseBidiMap() {
             return TreeBidiMap.this;
         }

         @Override
         public boolean equals(final Object obj) {
             return TreeBidiMap.this.doEquals(obj, DataElement.VALUE);
         }

         @Override
         public int hashCode() {
             return TreeBidiMap.this.doHashCode(DataElement.VALUE);
         }

         @Override
         public String toString() {
             return TreeBidiMap.this.doToString(DataElement.VALUE);
         }
     }

 }