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Commons Collections example source code file (MultiKeyMap.java)

This example Commons Collections source code file (MultiKeyMap.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

abstracthashedmap, hashedmap, illegalargumentexception, io, key, map, mapiterator, mapiterator, multikey, multikey, multikeymap, multikeymap, object, object, set, util

The Commons Collections MultiKeyMap.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.map;

import java.io.Serializable;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import org.apache.commons.collections.IterableMap;
import org.apache.commons.collections.MapIterator;
import org.apache.commons.collections.keyvalue.MultiKey;

/**
 * A <code>Map implementation that uses multiple keys to map the value.
 * <p>
 * This class is the most efficient way to uses multiple keys to map to a value.
 * The best way to use this class is via the additional map-style methods.
 * These provide <code>get, containsKey, put and
 * <code>remove for individual keys which operate without extra object creation.
 * <p>
 * The additional methods are the main interface of this map.
 * As such, you will not normally hold this map in a variable of type <code>Map.
 * <p>
 * The normal map methods take in and return a {@link MultiKey}.
 * If you try to use <code>put() with any other object type a
 * <code>ClassCastException is thrown. If you try to use null as
 * the key in <code>put() a NullPointerException is thrown.
 * <p>
 * This map is implemented as a decorator of a <code>AbstractHashedMap which
 * enables extra behaviour to be added easily.
 * <ul>
 * <li>MultiKeyMap.decorate(new LinkedMap()) creates an ordered map.
 * <li>MultiKeyMap.decorate(new LRUMap()) creates an least recently used map.
 * <li>MultiKeyMap.decorate(new ReferenceMap()) creates a garbage collector sensitive map.
 * </ul>
 * Note that <code>IdentityMap and ReferenceIdentityMap are unsuitable
 * for use as the key comparison would work on the whole MultiKey, not the elements within.
 * <p>
 * As an example, consider a least recently used cache that uses a String airline code
 * and a Locale to lookup the airline's name:
 * <pre>
 * private MultiKeyMap cache = MultiKeyMap.decorate(new LRUMap(50));
 * 
 * public String getAirlineName(String code, String locale) {
 *   String name = (String) cache.get(code, locale);
 *   if (name == null) {
 *     name = getAirlineNameFromDB(code, locale);
 *     cache.put(code, locale, name);
 *   }
 *   return name;
 * }
 * </pre>
 * <p>
 * <strong>Note that MultiKeyMap is not synchronized and is not thread-safe.
 * If you wish to use this map from multiple threads concurrently, you must use
 * appropriate synchronization. This class may throw exceptions when accessed
 * by concurrent threads without synchronization.
 *
 * @since Commons Collections 3.1
 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
 *
 * @author Stephen Colebourne
 */
public class MultiKeyMap
        implements IterableMap, Serializable {

    /** Serialisation version */
    private static final long serialVersionUID = -1788199231038721040L;

    /** The decorated map */
    protected final AbstractHashedMap map;

    //-----------------------------------------------------------------------
    /**
     * Decorates the specified map to add the MultiKeyMap API and fast query.
     * The map must not be null and must be empty.
     *
     * @param map  the map to decorate, not null
     * @throws IllegalArgumentException if the map is null or not empty
     */
    public static MultiKeyMap decorate(AbstractHashedMap map) {
        if (map == null) {
            throw new IllegalArgumentException("Map must not be null");
        }
        if (map.size() > 0) {
            throw new IllegalArgumentException("Map must be empty");
        }
        return new MultiKeyMap(map);
    }

    //-----------------------------------------------------------------------    
    /**
     * Constructs a new MultiKeyMap that decorates a <code>HashedMap.
     */
    public MultiKeyMap() {
        super();
        map = new HashedMap();
    }

    /**
     * Constructor that decorates the specified map and is called from
     * {@link #decorate(AbstractHashedMap)}.
     * The map must not be null and should be empty or only contain valid keys.
     * This constructor performs no validation.
     *
     * @param map  the map to decorate
     */
    protected MultiKeyMap(AbstractHashedMap map) {
        super();
        this.map = map;
    }

    //-----------------------------------------------------------------------
    /**
     * Gets the value mapped to the specified multi-key.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @return the mapped value, null if no match
     */
    public Object get(Object key1, Object key2) {
        int hashCode = hash(key1, key2);
        AbstractHashedMap.HashEntry entry = map.data[map.hashIndex(hashCode, map.data.length)];
        while (entry != null) {
            if (entry.hashCode == hashCode && isEqualKey(entry, key1, key2)) {
                return entry.getValue();
            }
            entry = entry.next;
        }
        return null;
    }

    /**
     * Checks whether the map contains the specified multi-key.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @return true if the map contains the key
     */
    public boolean containsKey(Object key1, Object key2) {
        int hashCode = hash(key1, key2);
        AbstractHashedMap.HashEntry entry = map.data[map.hashIndex(hashCode, map.data.length)];
        while (entry != null) {
            if (entry.hashCode == hashCode && isEqualKey(entry, key1, key2)) {
                return true;
            }
            entry = entry.next;
        }
        return false;
    }

    /**
     * Stores the value against the specified multi-key.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @param value  the value to store
     * @return the value previously mapped to this combined key, null if none
     */
    public Object put(Object key1, Object key2, Object value) {
        int hashCode = hash(key1, key2);
        int index = map.hashIndex(hashCode, map.data.length);
        AbstractHashedMap.HashEntry entry = map.data[index];
        while (entry != null) {
            if (entry.hashCode == hashCode && isEqualKey(entry, key1, key2)) {
                Object oldValue = entry.getValue();
                map.updateEntry(entry, value);
                return oldValue;
            }
            entry = entry.next;
        }
        
        map.addMapping(index, hashCode, new MultiKey(key1, key2), value);
        return null;
    }

    /**
     * Removes the specified multi-key from this map.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @return the value mapped to the removed key, null if key not in map
     */
    public Object remove(Object key1, Object key2) {
        int hashCode = hash(key1, key2);
        int index = map.hashIndex(hashCode, map.data.length);
        AbstractHashedMap.HashEntry entry = map.data[index];
        AbstractHashedMap.HashEntry previous = null;
        while (entry != null) {
            if (entry.hashCode == hashCode && isEqualKey(entry, key1, key2)) {
                Object oldValue = entry.getValue();
                map.removeMapping(entry, index, previous);
                return oldValue;
            }
            previous = entry;
            entry = entry.next;
        }
        return null;
    }

    /**
     * Gets the hash code for the specified multi-key.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @return the hash code
     */
    protected int hash(Object key1, Object key2) {
        int h = 0;
        if (key1 != null) {
            h ^= key1.hashCode();
        }
        if (key2 != null) {
            h ^= key2.hashCode();
        }
        h += ~(h << 9);
        h ^=  (h >>> 14);
        h +=  (h << 4);
        h ^=  (h >>> 10);
        return h;
    }

    /**
     * Is the key equal to the combined key.
     * 
     * @param entry  the entry to compare to
     * @param key1  the first key
     * @param key2  the second key
     * @return true if the key matches
     */
    protected boolean isEqualKey(AbstractHashedMap.HashEntry entry, Object key1, Object key2) {
        MultiKey multi = (MultiKey) entry.getKey();
        return
            multi.size() == 2 &&
            (key1 == null ? multi.getKey(0) == null : key1.equals(multi.getKey(0))) &&
            (key2 == null ? multi.getKey(1) == null : key2.equals(multi.getKey(1)));
    }

    //-----------------------------------------------------------------------
    /**
     * Gets the value mapped to the specified multi-key.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @param key3  the third key
     * @return the mapped value, null if no match
     */
    public Object get(Object key1, Object key2, Object key3) {
        int hashCode = hash(key1, key2, key3);
        AbstractHashedMap.HashEntry entry = map.data[map.hashIndex(hashCode, map.data.length)];
        while (entry != null) {
            if (entry.hashCode == hashCode && isEqualKey(entry, key1, key2, key3)) {
                return entry.getValue();
            }
            entry = entry.next;
        }
        return null;
    }

    /**
     * Checks whether the map contains the specified multi-key.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @param key3  the third key
     * @return true if the map contains the key
     */
    public boolean containsKey(Object key1, Object key2, Object key3) {
        int hashCode = hash(key1, key2, key3);
        AbstractHashedMap.HashEntry entry = map.data[map.hashIndex(hashCode, map.data.length)];
        while (entry != null) {
            if (entry.hashCode == hashCode && isEqualKey(entry, key1, key2, key3)) {
                return true;
            }
            entry = entry.next;
        }
        return false;
    }

    /**
     * Stores the value against the specified multi-key.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @param key3  the third key
     * @param value  the value to store
     * @return the value previously mapped to this combined key, null if none
     */
    public Object put(Object key1, Object key2, Object key3, Object value) {
        int hashCode = hash(key1, key2, key3);
        int index = map.hashIndex(hashCode, map.data.length);
        AbstractHashedMap.HashEntry entry = map.data[index];
        while (entry != null) {
            if (entry.hashCode == hashCode && isEqualKey(entry, key1, key2, key3)) {
                Object oldValue = entry.getValue();
                map.updateEntry(entry, value);
                return oldValue;
            }
            entry = entry.next;
        }
        
        map.addMapping(index, hashCode, new MultiKey(key1, key2, key3), value);
        return null;
    }

    /**
     * Removes the specified multi-key from this map.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @param key3  the third key
     * @return the value mapped to the removed key, null if key not in map
     */
    public Object remove(Object key1, Object key2, Object key3) {
        int hashCode = hash(key1, key2, key3);
        int index = map.hashIndex(hashCode, map.data.length);
        AbstractHashedMap.HashEntry entry = map.data[index];
        AbstractHashedMap.HashEntry previous = null;
        while (entry != null) {
            if (entry.hashCode == hashCode && isEqualKey(entry, key1, key2, key3)) {
                Object oldValue = entry.getValue();
                map.removeMapping(entry, index, previous);
                return oldValue;
            }
            previous = entry;
            entry = entry.next;
        }
        return null;
    }

    /**
     * Gets the hash code for the specified multi-key.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @param key3  the third key
     * @return the hash code
     */
    protected int hash(Object key1, Object key2, Object key3) {
        int h = 0;
        if (key1 != null) {
            h ^= key1.hashCode();
        }
        if (key2 != null) {
            h ^= key2.hashCode();
        }
        if (key3 != null) {
            h ^= key3.hashCode();
        }
        h += ~(h << 9);
        h ^=  (h >>> 14);
        h +=  (h << 4);
        h ^=  (h >>> 10);
        return h;
    }

    /**
     * Is the key equal to the combined key.
     * 
     * @param entry  the entry to compare to
     * @param key1  the first key
     * @param key2  the second key
     * @param key3  the third key
     * @return true if the key matches
     */
    protected boolean isEqualKey(AbstractHashedMap.HashEntry entry, Object key1, Object key2, Object key3) {
        MultiKey multi = (MultiKey) entry.getKey();
        return
            multi.size() == 3 &&
            (key1 == null ? multi.getKey(0) == null : key1.equals(multi.getKey(0))) &&
            (key2 == null ? multi.getKey(1) == null : key2.equals(multi.getKey(1))) &&
            (key3 == null ? multi.getKey(2) == null : key3.equals(multi.getKey(2)));
    }

    //-----------------------------------------------------------------------
    /**
     * Gets the value mapped to the specified multi-key.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @param key3  the third key
     * @param key4  the fourth key
     * @return the mapped value, null if no match
     */
    public Object get(Object key1, Object key2, Object key3, Object key4) {
        int hashCode = hash(key1, key2, key3, key4);
        AbstractHashedMap.HashEntry entry = map.data[map.hashIndex(hashCode, map.data.length)];
        while (entry != null) {
            if (entry.hashCode == hashCode && isEqualKey(entry, key1, key2, key3, key4)) {
                return entry.getValue();
            }
            entry = entry.next;
        }
        return null;
    }

    /**
     * Checks whether the map contains the specified multi-key.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @param key3  the third key
     * @param key4  the fourth key
     * @return true if the map contains the key
     */
    public boolean containsKey(Object key1, Object key2, Object key3, Object key4) {
        int hashCode = hash(key1, key2, key3, key4);
        AbstractHashedMap.HashEntry entry = map.data[map.hashIndex(hashCode, map.data.length)];
        while (entry != null) {
            if (entry.hashCode == hashCode && isEqualKey(entry, key1, key2, key3, key4)) {
                return true;
            }
            entry = entry.next;
        }
        return false;
    }

    /**
     * Stores the value against the specified multi-key.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @param key3  the third key
     * @param key4  the fourth key
     * @param value  the value to store
     * @return the value previously mapped to this combined key, null if none
     */
    public Object put(Object key1, Object key2, Object key3, Object key4, Object value) {
        int hashCode = hash(key1, key2, key3, key4);
        int index = map.hashIndex(hashCode, map.data.length);
        AbstractHashedMap.HashEntry entry = map.data[index];
        while (entry != null) {
            if (entry.hashCode == hashCode && isEqualKey(entry, key1, key2, key3, key4)) {
                Object oldValue = entry.getValue();
                map.updateEntry(entry, value);
                return oldValue;
            }
            entry = entry.next;
        }
        
        map.addMapping(index, hashCode, new MultiKey(key1, key2, key3, key4), value);
        return null;
    }

    /**
     * Removes the specified multi-key from this map.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @param key3  the third key
     * @param key4  the fourth key
     * @return the value mapped to the removed key, null if key not in map
     */
    public Object remove(Object key1, Object key2, Object key3, Object key4) {
        int hashCode = hash(key1, key2, key3, key4);
        int index = map.hashIndex(hashCode, map.data.length);
        AbstractHashedMap.HashEntry entry = map.data[index];
        AbstractHashedMap.HashEntry previous = null;
        while (entry != null) {
            if (entry.hashCode == hashCode && isEqualKey(entry, key1, key2, key3, key4)) {
                Object oldValue = entry.getValue();
                map.removeMapping(entry, index, previous);
                return oldValue;
            }
            previous = entry;
            entry = entry.next;
        }
        return null;
    }

    /**
     * Gets the hash code for the specified multi-key.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @param key3  the third key
     * @param key4  the fourth key
     * @return the hash code
     */
    protected int hash(Object key1, Object key2, Object key3, Object key4) {
        int h = 0;
        if (key1 != null) {
            h ^= key1.hashCode();
        }
        if (key2 != null) {
            h ^= key2.hashCode();
        }
        if (key3 != null) {
            h ^= key3.hashCode();
        }
        if (key4 != null) {
            h ^= key4.hashCode();
        }
        h += ~(h << 9);
        h ^=  (h >>> 14);
        h +=  (h << 4);
        h ^=  (h >>> 10);
        return h;
    }

    /**
     * Is the key equal to the combined key.
     * 
     * @param entry  the entry to compare to
     * @param key1  the first key
     * @param key2  the second key
     * @param key3  the third key
     * @param key4  the fourth key
     * @return true if the key matches
     */
    protected boolean isEqualKey(AbstractHashedMap.HashEntry entry, Object key1, Object key2, Object key3, Object key4) {
        MultiKey multi = (MultiKey) entry.getKey();
        return
            multi.size() == 4 &&
            (key1 == null ? multi.getKey(0) == null : key1.equals(multi.getKey(0))) &&
            (key2 == null ? multi.getKey(1) == null : key2.equals(multi.getKey(1))) &&
            (key3 == null ? multi.getKey(2) == null : key3.equals(multi.getKey(2))) &&
            (key4 == null ? multi.getKey(3) == null : key4.equals(multi.getKey(3)));
    }

    //-----------------------------------------------------------------------
    /**
     * Gets the value mapped to the specified multi-key.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @param key3  the third key
     * @param key4  the fourth key
     * @param key5  the fifth key
     * @return the mapped value, null if no match
     */
    public Object get(Object key1, Object key2, Object key3, Object key4, Object key5) {
        int hashCode = hash(key1, key2, key3, key4, key5);
        AbstractHashedMap.HashEntry entry = map.data[map.hashIndex(hashCode, map.data.length)];
        while (entry != null) {
            if (entry.hashCode == hashCode && isEqualKey(entry, key1, key2, key3, key4, key5)) {
                return entry.getValue();
            }
            entry = entry.next;
        }
        return null;
    }

    /**
     * Checks whether the map contains the specified multi-key.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @param key3  the third key
     * @param key4  the fourth key
     * @param key5  the fifth key
     * @return true if the map contains the key
     */
    public boolean containsKey(Object key1, Object key2, Object key3, Object key4, Object key5) {
        int hashCode = hash(key1, key2, key3, key4, key5);
        AbstractHashedMap.HashEntry entry = map.data[map.hashIndex(hashCode, map.data.length)];
        while (entry != null) {
            if (entry.hashCode == hashCode && isEqualKey(entry, key1, key2, key3, key4, key5)) {
                return true;
            }
            entry = entry.next;
        }
        return false;
    }

    /**
     * Stores the value against the specified multi-key.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @param key3  the third key
     * @param key4  the fourth key
     * @param key5  the fifth key
     * @param value  the value to store
     * @return the value previously mapped to this combined key, null if none
     */
    public Object put(Object key1, Object key2, Object key3, Object key4, Object key5, Object value) {
        int hashCode = hash(key1, key2, key3, key4, key5);
        int index = map.hashIndex(hashCode, map.data.length);
        AbstractHashedMap.HashEntry entry = map.data[index];
        while (entry != null) {
            if (entry.hashCode == hashCode && isEqualKey(entry, key1, key2, key3, key4, key5)) {
                Object oldValue = entry.getValue();
                map.updateEntry(entry, value);
                return oldValue;
            }
            entry = entry.next;
        }
        
        map.addMapping(index, hashCode, new MultiKey(key1, key2, key3, key4, key5), value);
        return null;
    }

    /**
     * Removes the specified multi-key from this map.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @param key3  the third key
     * @param key4  the fourth key
     * @param key5  the fifth key
     * @return the value mapped to the removed key, null if key not in map
     */
    public Object remove(Object key1, Object key2, Object key3, Object key4, Object key5) {
        int hashCode = hash(key1, key2, key3, key4, key5);
        int index = map.hashIndex(hashCode, map.data.length);
        AbstractHashedMap.HashEntry entry = map.data[index];
        AbstractHashedMap.HashEntry previous = null;
        while (entry != null) {
            if (entry.hashCode == hashCode && isEqualKey(entry, key1, key2, key3, key4, key5)) {
                Object oldValue = entry.getValue();
                map.removeMapping(entry, index, previous);
                return oldValue;
            }
            previous = entry;
            entry = entry.next;
        }
        return null;
    }

    /**
     * Gets the hash code for the specified multi-key.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @param key3  the third key
     * @param key4  the fourth key
     * @param key5  the fifth key
     * @return the hash code
     */
    protected int hash(Object key1, Object key2, Object key3, Object key4, Object key5) {
        int h = 0;
        if (key1 != null) {
            h ^= key1.hashCode();
        }
        if (key2 != null) {
            h ^= key2.hashCode();
        }
        if (key3 != null) {
            h ^= key3.hashCode();
        }
        if (key4 != null) {
            h ^= key4.hashCode();
        }
        if (key5 != null) {
            h ^= key5.hashCode();
        }
        h += ~(h << 9);
        h ^=  (h >>> 14);
        h +=  (h << 4);
        h ^=  (h >>> 10);
        return h;
    }

    /**
     * Is the key equal to the combined key.
     * 
     * @param entry  the entry to compare to
     * @param key1  the first key
     * @param key2  the second key
     * @param key3  the third key
     * @param key4  the fourth key
     * @param key5  the fifth key
     * @return true if the key matches
     */
    protected boolean isEqualKey(AbstractHashedMap.HashEntry entry, Object key1, Object key2, Object key3, Object key4, Object key5) {
        MultiKey multi = (MultiKey) entry.getKey();
        return
            multi.size() == 5 &&
            (key1 == null ? multi.getKey(0) == null : key1.equals(multi.getKey(0))) &&
            (key2 == null ? multi.getKey(1) == null : key2.equals(multi.getKey(1))) &&
            (key3 == null ? multi.getKey(2) == null : key3.equals(multi.getKey(2))) &&
            (key4 == null ? multi.getKey(3) == null : key4.equals(multi.getKey(3))) &&
            (key5 == null ? multi.getKey(4) == null : key5.equals(multi.getKey(4)));
    }

    //-----------------------------------------------------------------------
    /**
     * Removes all mappings where the first key is that specified.
     * <p>
     * This method removes all the mappings where the <code>MultiKey
     * has one or more keys, and the first matches that specified.
     * 
     * @param key1  the first key
     * @return true if any elements were removed
     */
    public boolean removeAll(Object key1) {
        boolean modified = false;
        MapIterator it = mapIterator();
        while (it.hasNext()) {
            MultiKey multi = (MultiKey) it.next();
            if (multi.size() >= 1 &&
                (key1 == null ? multi.getKey(0) == null : key1.equals(multi.getKey(0)))) {
                it.remove();
                modified = true;
            }
        }
        return modified;
    }

    /**
     * Removes all mappings where the first two keys are those specified.
     * <p>
     * This method removes all the mappings where the <code>MultiKey
     * has two or more keys, and the first two match those specified.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @return true if any elements were removed
     */
    public boolean removeAll(Object key1, Object key2) {
        boolean modified = false;
        MapIterator it = mapIterator();
        while (it.hasNext()) {
            MultiKey multi = (MultiKey) it.next();
            if (multi.size() >= 2 &&
                (key1 == null ? multi.getKey(0) == null : key1.equals(multi.getKey(0))) &&
                (key2 == null ? multi.getKey(1) == null : key2.equals(multi.getKey(1)))) {
                it.remove();
                modified = true;
            }
        }
        return modified;
    }

    /**
     * Removes all mappings where the first three keys are those specified.
     * <p>
     * This method removes all the mappings where the <code>MultiKey
     * has three or more keys, and the first three match those specified.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @param key3  the third key
     * @return true if any elements were removed
     */
    public boolean removeAll(Object key1, Object key2, Object key3) {
        boolean modified = false;
        MapIterator it = mapIterator();
        while (it.hasNext()) {
            MultiKey multi = (MultiKey) it.next();
            if (multi.size() >= 3 &&
                (key1 == null ? multi.getKey(0) == null : key1.equals(multi.getKey(0))) &&
                (key2 == null ? multi.getKey(1) == null : key2.equals(multi.getKey(1))) &&
                (key3 == null ? multi.getKey(2) == null : key3.equals(multi.getKey(2)))) {
                it.remove();
                modified = true;
            }
        }
        return modified;
    }

    /**
     * Removes all mappings where the first four keys are those specified.
     * <p>
     * This method removes all the mappings where the <code>MultiKey
     * has four or more keys, and the first four match those specified.
     * 
     * @param key1  the first key
     * @param key2  the second key
     * @param key3  the third key
     * @param key4  the fourth key
     * @return true if any elements were removed
     */
    public boolean removeAll(Object key1, Object key2, Object key3, Object key4) {
        boolean modified = false;
        MapIterator it = mapIterator();
        while (it.hasNext()) {
            MultiKey multi = (MultiKey) it.next();
            if (multi.size() >= 4 &&
                (key1 == null ? multi.getKey(0) == null : key1.equals(multi.getKey(0))) &&
                (key2 == null ? multi.getKey(1) == null : key2.equals(multi.getKey(1))) &&
                (key3 == null ? multi.getKey(2) == null : key3.equals(multi.getKey(2))) &&
                (key4 == null ? multi.getKey(3) == null : key4.equals(multi.getKey(3)))) {
                it.remove();
                modified = true;
            }
        }
        return modified;
    }

    //-----------------------------------------------------------------------
    /**
     * Check to ensure that input keys are valid MultiKey objects.
     * 
     * @param key  the key to check
     */
    protected void checkKey(Object key) {
        if (key == null) {
            throw new NullPointerException("Key must not be null");
        }
        if (key instanceof MultiKey == false) {
            throw new ClassCastException("Key must be a MultiKey");
        }
    }

    /**
     * Clones the map without cloning the keys or values.
     *
     * @return a shallow clone
     */
    public Object clone() {
        return new MultiKeyMap((AbstractHashedMap) map.clone());
    }

    /**
     * Puts the key and value into the map, where the key must be a non-null
     * MultiKey object.
     * 
     * @param key  the non-null MultiKey object
     * @param value  the value to store
     * @return the previous value for the key
     * @throws NullPointerException if the key is null
     * @throws ClassCastException if the key is not a MultiKey
     */
    public Object put(Object key, Object value) {
        checkKey(key);
        return map.put(key, value);
    }

    /**
     * Copies all of the keys and values from the specified map to this map.
     * Each key must be non-null and a MultiKey object.
     * 
     * @param mapToCopy  to this map
     * @throws NullPointerException if the mapToCopy or any key within is null
     * @throws ClassCastException if any key in mapToCopy is not a MultiKey
     */
    public void putAll(Map mapToCopy) {
        for (Iterator it = mapToCopy.keySet().iterator(); it.hasNext();) {
            Object key = it.next();
            checkKey(key);
        }
        map.putAll(mapToCopy);
    }

    //-----------------------------------------------------------------------
    public MapIterator mapIterator() {
        return map.mapIterator();
    }

    public int size() {
        return map.size();
    }

    public boolean isEmpty() {
        return map.isEmpty();
    }

    public boolean containsKey(Object key) {
        return map.containsKey(key);
    }

    public boolean containsValue(Object value) {
        return map.containsValue(value);
    }

    public Object get(Object key) {
        return map.get(key);
    }

    public Object remove(Object key) {
        return map.remove(key);
    }

    public void clear() {
        map.clear();
    }

    public Set keySet() {
        return map.keySet();
    }

    public Collection values() {
        return map.values();
    }

    public Set entrySet() {
        return map.entrySet();
    }

    public boolean equals(Object obj) {
        if (obj == this) {
            return true;
        }
        return map.equals(obj);
    }

    public int hashCode() {
        return map.hashCode();
    }

    public String toString() {
        return map.toString();
    }

}

Other Commons Collections examples (source code examples)

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

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