binarytree.java

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/* ====================================================================
   Copyright 2002-2004   Apache Software Foundation

   Licensed 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.poi.util;

import java.util.*;

/**
 * Red-Black tree-based implementation of Map. 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,
 * particularly when trying to keep the two TreeMaps synchronized with
 * each other. And if the data contained in the TreeMaps is large, the
 * cost of redundant storage becomes significant.<p>
 *
 * This solution keeps the data properly synchronized and minimizes
 * the data storage. The red-black algorithm is based on TreeMap's,
 * 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>
 *
 * There are some limitations placed on data kept in this Map. The
 * biggest one is this:<p>
 *
 * When performing a put operation, neither the key nor the value may
 * already exist in the Map. In the java.util Map implementations
 * (HashMap, TreeMap), you can perform a put with an already mapped
 * key, and neither cares about duplicate values at all ... but this
 * implementation's put method with throw an IllegalArgumentException
 * if either the key or the value is already in the Map.<p>
 *
 * Obviously, that same restriction (and consequence of failing to
 * heed that restriction) applies to the putAll method.<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.<p>
 *
 * New methods are added to take advantage of the fact that values are
 * kept sorted independently of their keys:<p>
 *
 * Object getKeyForValue(Object value) is the opposite of get; it
 * takes a value and returns its key, if any.<p>
 *
 * Object removeValue(Object value) finds and removes the specified
 * value and returns the now un-used key.<p>
 *
 * Set entrySetByValue() returns the Map.Entry's in a Set whose
 * iterator will iterate over the Map.Entry's in ascending order by
 * their corresponding values.<p>
 *
 * Set keySetByValue() returns the keys in a Set whose iterator will
 * iterate over the keys in ascending order by their corresponding
 * values.<p>
 *
 * Collection valuesByValue() returns the values in a Collection whose
 * iterator will iterate over the values in ascending order.<p>
 *
 * @author Marc Johnson (mjohnson at apache dot org)
 */
public final class BinaryTree   // final for performance

    extends AbstractMap
{
    private Node[]                _root             = new Node[]
    {
        null, null
    };
    private int                   _size             = 0;
    private int                   _modifications    = 0;
    private Set[]                 _key_set          = new Set[]
    {
        null, null
    };
    private Set[]                 _entry_set        = new Set[]
    {
        null, null
    };
    private Collection[]          _value_collection = new Collection[]
    {
        null, null
    };
    private static final int      _KEY              = 0;
    private static final int      _VALUE            = 1;
    private static final int      _INDEX_SUM        = _KEY + _VALUE;
    private static final int      _MINIMUM_INDEX    = 0;
    private static final int      _INDEX_COUNT      = 2;
    private static final String[] _data_name        = new String[]
    {
        "key", "value"
    };

    /**
     * Construct a new BinaryTree
     */

    public BinaryTree()
    {
    }

    /**
     * Constructs a new BinaryTree from an existing Map, with keys and
     * values sorted
     *
     * @param map the map whose mappings are to be placed in this map.
     *
     * @exception ClassCastException if the keys in the map are not
     *                               Comparable, or are not mutually
     *                               comparable; also if the values in
     *                               the map are not Comparable, or
     *                               are not mutually Comparable
     * @exception NullPointerException if any key or value in the map
     *                                 is null
     * @exception IllegalArgumentException if there are duplicate keys
     *                                     or duplicate values in the
     *                                     map
     */

    public BinaryTree(final Map map)
        throws ClassCastException, NullPointerException,
                IllegalArgumentException
    {
        putAll(map);
    }

    /**
     * Returns the key to which this map maps the specified value.
     * Returns null if the map contains no mapping for this value.
     *
     * @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.
     *
     * @exception ClassCastException if the value is of an
     *                               inappropriate type for this map.
     * @exception NullPointerException if the value is null
     */

    public Object getKeyForValue(final Object value)
        throws ClassCastException, NullPointerException
    {
        return doGet(( Comparable ) value, _VALUE);
    }

    /**
     * Removes the mapping for this value from this map if present
     *
     * @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.
     */

    public Object removeValue(final Object value)
    {
        return doRemove(( Comparable ) value, _VALUE);
    }

    /**
     * Returns a set view of the mappings contained in this map. Each
     * element in the returned set is a Map.Entry. 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. The set supports element removal, which removes the
     * corresponding mapping from the map, via the Iterator.remove,
     * Set.remove, removeAll, retainAll and clear operations.  It does
     * not support the add or addAll operations.<p>
     *
     * The difference between this method and entrySet is that
     * entrySet's iterator() method returns an iterator that iterates
     * over the mappings in ascending order by key. This method's
     * iterator method iterates over the mappings in ascending order
     * by value.
     *
     * @return a set view of the mappings contained in this map.
     */

    public Set entrySetByValue()
    {
        if (_entry_set[ _VALUE ] == null)
        {
            _entry_set[ _VALUE ] = new AbstractSet()
            {
                public Iterator iterator()
                {
                    return new BinaryTreeIterator(_VALUE)
                    {
                        protected Object doGetNext()
                        {
                            return _last_returned_node;
                        }
                    };
                }

                public boolean contains(Object o)
                {
                    if (!(o instanceof Map.Entry))
                    {
                        return false;
                    }
                    Map.Entry entry = ( Map.Entry ) o;
                    Object    key   = entry.getKey();
                    Node      node  = lookup(( Comparable ) entry.getValue(),
                                             _VALUE);

                    return (node != null) && node.getData(_KEY).equals(key);
                }

                public boolean remove(Object o)
                {
                    if (!(o instanceof Map.Entry))
                    {
                        return false;
                    }
                    Map.Entry entry = ( Map.Entry ) o;
                    Object    key   = entry.getKey();
                    Node      node  = lookup(( Comparable ) entry.getValue(),
                                             _VALUE);

                    if ((node != null) && node.getData(_KEY).equals(key))
                    {
                        doRedBlackDelete(node);
                        return true;
                    }
                    return false;
                }

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

                public void clear()
                {
                    BinaryTree.this.clear();
                }
            };
        }
        return _entry_set[ _VALUE ];
    }

    /**
     * Returns a set view of the keys contained in this map.  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. The set supports element removal,
     * which removes the corresponding mapping from the map, via the
     * Iterator.remove, Set.remove, removeAll, retainAll, and clear
     * operations. It does not support the add or addAll
     * operations.<p>
     *
     * The difference between this method and keySet is that keySet's
     * iterator() method returns an iterator that iterates over the
     * keys in ascending order by key. This method's iterator method
     * iterates over the keys in ascending order by value.
     *
     * @return a set view of the keys contained in this map.
     */

    public Set keySetByValue()
    {
        if (_key_set[ _VALUE ] == null)
        {
            _key_set[ _VALUE ] = new AbstractSet()
            {
                public Iterator iterator()
                {
                    return new BinaryTreeIterator(_VALUE)
                    {
                        protected Object doGetNext()
                        {
                            return _last_returned_node.getData(_KEY);
                        }
                    };
                }

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

                public boolean contains(Object o)
                {
                    return containsKey(o);
                }

                public boolean remove(Object o)
                {
                    int old_size = _size;

                    BinaryTree.this.remove(o);
                    return _size != old_size;
                }

                public void clear()
                {
                    BinaryTree.this.clear();
                }
            };
        }
        return _key_set[ _VALUE ];
    }

    /**
     * Returns a collection view of the values contained in this
     * map. The collection is backed by the map, so changes to the map
     * are reflected in the collection, and vice-versa. If the map is
     * modified while an iteration over the collection is in progress,
     * the results of the iteration are undefined. The collection
     * supports element removal, which removes the corresponding
     * mapping from the map, via the Iterator.remove,
     * Collection.remove, removeAll, retainAll and clear operations.
     * It does not support the add or addAll operations.<p>
     *
     * The difference between this method and values is that values's
     * iterator() method returns an iterator that iterates over the
     * values in ascending order by key. This method's iterator method
     * iterates over the values in ascending order by key.
     *
     * @return a collection view of the values contained in this map.
     */

    public Collection valuesByValue()
    {
        if (_value_collection[ _VALUE ] == null)
        {
            _value_collection[ _VALUE ] = new AbstractCollection()
            {
                public Iterator iterator()
                {
                    return new BinaryTreeIterator(_VALUE)
                    {
                        protected Object doGetNext()
                        {
                            return _last_returned_node.getData(_VALUE);
                        }
                    };
                }

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

                public boolean contains(Object o)
                {
                    return containsValue(o);
                }

                public boolean remove(Object o)
                {
                    int old_size = _size;

                    removeValue(o);
                    return _size != old_size;
                }

                public boolean removeAll(Collection c)
                {
                    boolean  modified = false;
                    Iterator iter     = c.iterator();

                    while (iter.hasNext())
                    {
                        if (removeValue(iter.next()) != null)
                        {
                            modified = true;
                        }
                    }
                    return modified;
                }