home | career | drupal | java | mac | mysql | perl | scala | uml | unix  

Commons Collections example source code file (DualTreeBidiMap.java)

This example Commons Collections source code file (DualTreeBidiMap.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Commons Collections tags/keywords

bidimap, dualtreebidimap, dualtreebidimap, io, iterator, map, object, object, orderedmap, sortedbidimap, sortedmap, sortedmap, treemap, treemap, util, viewmap

The Commons Collections DualTreeBidiMap.java source code

/*
 *  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.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.Iterator;
import java.util.ListIterator;
import java.util.Map;
import java.util.SortedMap;
import java.util.TreeMap;

import org.apache.commons.collections.BidiMap;
import org.apache.commons.collections.OrderedBidiMap;
import org.apache.commons.collections.OrderedMap;
import org.apache.commons.collections.OrderedMapIterator;
import org.apache.commons.collections.ResettableIterator;
import org.apache.commons.collections.SortedBidiMap;
import org.apache.commons.collections.map.AbstractSortedMapDecorator;

/**
 * Implementation of <code>BidiMap that uses two TreeMap instances.
 * <p>
 * The setValue() method on iterators will succeed only if the new value being set is
 * not already in the bidimap.
 * <p>
 * When considering whether to use this class, the {@link TreeBidiMap} class should
 * also be considered. It implements the interface using a dedicated design, and does
 * not store each object twice, which can save on memory use.
 * <p>
 * NOTE: From Commons Collections 3.1, all subclasses will use <code>TreeMap
 * and the flawed <code>createMap method is ignored.
 * 
 * @since Commons Collections 3.0
 * @version $Id: DualTreeBidiMap.java 646777 2008-04-10 12:33:15Z niallp $
 * 
 * @author Matthew Hawthorne
 * @author Stephen Colebourne
 */
public class DualTreeBidiMap
        extends AbstractDualBidiMap implements SortedBidiMap, Serializable {

    /** Ensure serialization compatibility */
    private static final long serialVersionUID = 721969328361809L;
    /** The comparator to use */
    protected final Comparator comparator;
    
    /**
     * Creates an empty <code>DualTreeBidiMap
     */
    public DualTreeBidiMap() {
        super(new TreeMap(), new TreeMap());
        this.comparator = null;
    }

    /** 
     * Constructs a <code>DualTreeBidiMap and copies the mappings from
     * specified <code>Map.  
     *
     * @param map  the map whose mappings are to be placed in this map
     */
    public DualTreeBidiMap(Map map) {
        super(new TreeMap(), new TreeMap());
        putAll(map);
        this.comparator = null;
    }

    /** 
     * Constructs a <code>DualTreeBidiMap using the specified Comparator.
     *
     * @param comparator  the Comparator
     */
    public DualTreeBidiMap(Comparator comparator) {
        super(new TreeMap(comparator), new TreeMap(comparator));
        this.comparator = comparator;
    }

    /** 
     * Constructs a <code>DualTreeBidiMap that decorates the specified maps.
     *
     * @param normalMap  the normal direction map
     * @param reverseMap  the reverse direction map
     * @param inverseBidiMap  the inverse BidiMap
     */
    protected DualTreeBidiMap(Map normalMap, Map reverseMap, BidiMap inverseBidiMap) {
        super(normalMap, reverseMap, inverseBidiMap);
        this.comparator = ((SortedMap) normalMap).comparator();
    }

    /**
     * Creates a new instance of this object.
     * 
     * @param normalMap  the normal direction map
     * @param reverseMap  the reverse direction map
     * @param inverseMap  the inverse BidiMap
     * @return new bidi map
     */
    protected BidiMap createBidiMap(Map normalMap, Map reverseMap, BidiMap inverseMap) {
        return new DualTreeBidiMap(normalMap, reverseMap, inverseMap);
    }

    //-----------------------------------------------------------------------
    public Comparator comparator() {
        return ((SortedMap) maps[0]).comparator();
    }

    public Object firstKey() {
        return ((SortedMap) maps[0]).firstKey();
    }

    public Object lastKey() {
        return ((SortedMap) maps[0]).lastKey();
    }

    public Object nextKey(Object key) {
        if (isEmpty()) {
            return null;
        }
        if (maps[0] instanceof OrderedMap) {
            return ((OrderedMap) maps[0]).nextKey(key);
        }
        SortedMap sm = (SortedMap) maps[0];
        Iterator it = sm.tailMap(key).keySet().iterator();
        it.next();
        if (it.hasNext()) {
            return it.next();
        }
        return null;
    }

    public Object previousKey(Object key) {
        if (isEmpty()) {
            return null;
        }
        if (maps[0] instanceof OrderedMap) {
            return ((OrderedMap) maps[0]).previousKey(key);
        }
        SortedMap sm = (SortedMap) maps[0];
        SortedMap hm = sm.headMap(key);
        if (hm.isEmpty()) {
            return null;
        }
        return hm.lastKey();
    }

    //-----------------------------------------------------------------------
    /**
     * Obtains an ordered map iterator.
     * <p>
     * This implementation copies the elements to an ArrayList in order to
     * provide the forward/backward behaviour.
     * 
     * @return a new ordered map iterator
     */
    public OrderedMapIterator orderedMapIterator() {
        return new BidiOrderedMapIterator(this);
    }

    public SortedBidiMap inverseSortedBidiMap() {
        return (SortedBidiMap) inverseBidiMap();
    }

    public OrderedBidiMap inverseOrderedBidiMap() {
        return (OrderedBidiMap) inverseBidiMap();
    }

    //-----------------------------------------------------------------------
    public SortedMap headMap(Object toKey) {
        SortedMap sub = ((SortedMap) maps[0]).headMap(toKey);
        return new ViewMap(this, sub);
    }

    public SortedMap tailMap(Object fromKey) {
        SortedMap sub = ((SortedMap) maps[0]).tailMap(fromKey);
        return new ViewMap(this, sub);
    }

    public SortedMap subMap(Object fromKey, Object toKey) {
        SortedMap sub = ((SortedMap) maps[0]).subMap(fromKey, toKey);
        return new ViewMap(this, sub);
    }
    
    //-----------------------------------------------------------------------
    /**
     * Internal sorted map view.
     */
    protected static class ViewMap extends AbstractSortedMapDecorator {
        /** The parent bidi map. */
        final DualTreeBidiMap bidi;
        
        /**
         * Constructor.
         * @param bidi  the parent bidi map
         * @param sm  the subMap sorted map
         */
        protected ViewMap(DualTreeBidiMap bidi, SortedMap sm) {
            // the implementation is not great here...
            // use the maps[0] as the filtered map, but maps[1] as the full map
            // this forces containsValue and clear to be overridden
            super((SortedMap) bidi.createBidiMap(sm, bidi.maps[1], bidi.inverseBidiMap));
            this.bidi = (DualTreeBidiMap) map;
        }
        
        public boolean containsValue(Object value) {
            // override as default implementation jumps to [1]
            return bidi.maps[0].containsValue(value);
        }
        
        public void clear() {
            // override as default implementation jumps to [1]
            for (Iterator it = keySet().iterator(); it.hasNext();) {
                it.next();
                it.remove();
            }
        }
        
        public SortedMap headMap(Object toKey) {
            return new ViewMap(bidi, super.headMap(toKey));
        }

        public SortedMap tailMap(Object fromKey) {
            return new ViewMap(bidi, super.tailMap(fromKey));
        }

        public SortedMap subMap(Object fromKey, Object toKey) {
            return new ViewMap(bidi, super.subMap(fromKey, toKey));
        }
    }

    //-----------------------------------------------------------------------
    /**
     * Inner class MapIterator.
     */
    protected static class BidiOrderedMapIterator implements OrderedMapIterator, ResettableIterator {
        
        /** The parent map */
        protected final AbstractDualBidiMap parent;
        /** The iterator being decorated */
        protected ListIterator iterator;
        /** The last returned entry */
        private Map.Entry last = null;
        
        /**
         * Constructor.
         * @param parent  the parent map
         */
        protected BidiOrderedMapIterator(AbstractDualBidiMap parent) {
            super();
            this.parent = parent;
            iterator = new ArrayList(parent.entrySet()).listIterator();
        }
        
        public boolean hasNext() {
            return iterator.hasNext();
        }
        
        public Object next() {
            last = (Map.Entry) iterator.next();
            return last.getKey();
        }
        
        public boolean hasPrevious() {
            return iterator.hasPrevious();
        }
        
        public Object previous() {
            last = (Map.Entry) iterator.previous();
            return last.getKey();
        }
        
        public void remove() {
            iterator.remove();
            parent.remove(last.getKey());
            last = null;
        }
        
        public Object getKey() {
            if (last == null) {
                throw new IllegalStateException("Iterator getKey() can only be called after next() and before remove()");
            }
            return last.getKey();
        }

        public Object getValue() {
            if (last == null) {
                throw new IllegalStateException("Iterator getValue() can only be called after next() and before remove()");
            }
            return last.getValue();
        }
        
        public Object setValue(Object value) {
            if (last == null) {
                throw new IllegalStateException("Iterator setValue() can only be called after next() and before remove()");
            }
            if (parent.maps[1].containsKey(value) &&
                parent.maps[1].get(value) != last.getKey()) {
                throw new IllegalArgumentException("Cannot use setValue() when the object being set is already in the map");
            }
            return parent.put(last.getKey(), value);
        }
        
        public void reset() {
            iterator = new ArrayList(parent.entrySet()).listIterator();
            last = null;
        }
        
        public String toString() {
            if (last != null) {
                return "MapIterator[" + getKey() + "=" + getValue() + "]";
            } else {
                return "MapIterator[]";
            }
        }
    }
    
    // Serialization
    //-----------------------------------------------------------------------
    private void writeObject(ObjectOutputStream out) throws IOException {
        out.defaultWriteObject();
        out.writeObject(maps[0]);
    }

    private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
        in.defaultReadObject();
        maps[0] = new TreeMap(comparator);
        maps[1] = new TreeMap(comparator);
        Map map = (Map) in.readObject();
        putAll(map);
    }

}

Other Commons Collections examples (source code examples)

Here is a short list of links related to this Commons Collections DualTreeBidiMap.java source code file:

new blog posts

 

Copyright 1998-2016 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.