org.apache.commons.collections.MultiHashMap Maven / Gradle / Ivy
/*
* 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;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.util.AbstractCollection;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;
import org.apache.commons.collections.iterators.EmptyIterator;
/**
* MultiHashMap is the default implementation of the
* {@link org.apache.commons.collections.MultiMap MultiMap} interface.
*
* A MultiMap is a Map with slightly different semantics.
* Putting a value into the map will add the value to a Collection at that key.
* Getting a value will return a Collection, holding all the values put to that key.
*
* This implementation uses an ArrayList as the collection.
* The internal storage list is made available without cloning via the
* get(Object) and entrySet() methods.
* The implementation returns null when there are no values mapped to a key.
*
* For example:
*
* MultiMap mhm = new MultiHashMap();
* mhm.put(key, "A");
* mhm.put(key, "B");
* mhm.put(key, "C");
* List list = (List) mhm.get(key);
*
* list will be a list containing "A", "B", "C".
*
* @deprecated Class now available as MultiValueMap in map subpackage.
* This version is due to be removed in collections v4.0.
*
* @since Commons Collections 2.0
* @version $Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
*
* @author Christopher Berry
* @author James Strachan
* @author Steve Downey
* @author Stephen Colebourne
* @author Julien Buret
* @author Serhiy Yevtushenko
* @author Robert Ribnitz
*/
public class MultiHashMap extends HashMap implements MultiMap {
// backed values collection
private transient Collection values = null;
// compatibility with commons-collection releases 2.0/2.1
private static final long serialVersionUID = 1943563828307035349L;
/**
* Constructor.
*/
public MultiHashMap() {
super();
}
/**
* Constructor.
*
* @param initialCapacity the initial map capacity
*/
public MultiHashMap(int initialCapacity) {
super(initialCapacity);
}
/**
* Constructor.
*
* @param initialCapacity the initial map capacity
* @param loadFactor the amount 0.0-1.0 at which to resize the map
*/
public MultiHashMap(int initialCapacity, float loadFactor) {
super(initialCapacity, loadFactor);
}
/**
* Constructor that copies the input map creating an independent copy.
*
* This method performs different behaviour depending on whether the map
* specified is a MultiMap or not. If a MultiMap is specified, each internal
* collection is also cloned. If the specified map only implements Map, then
* the values are not cloned.
*
* NOTE: From Commons Collections 3.1 this method correctly copies a MultiMap
* to form a truly independent new map.
* NOTE: From Commons Collections 3.2 this method delegates to the newly
* added putAll(Map) override method.
*
* @param mapToCopy a Map to copy
*/
public MultiHashMap(Map mapToCopy) {
// be careful of JDK 1.3 vs 1.4 differences
super((int) (mapToCopy.size() * 1.4f));
putAll(mapToCopy);
}
/**
* Read the object during deserialization.
*/
private void readObject(ObjectInputStream s) throws IOException, ClassNotFoundException {
// This method is needed because the 1.2/1.3 Java deserialisation called
// put and thus messed up that method
// default read object
s.defaultReadObject();
// problem only with jvm <1.4
String version = "1.2";
try {
version = System.getProperty("java.version");
} catch (SecurityException ex) {
// ignore and treat as 1.2/1.3
}
if (version.startsWith("1.2") || version.startsWith("1.3")) {
for (Iterator iterator = entrySet().iterator(); iterator.hasNext();) {
Map.Entry entry = (Map.Entry) iterator.next();
// put has created a extra collection level, remove it
super.put(entry.getKey(), ((Collection) entry.getValue()).iterator().next());
}
}
}
//-----------------------------------------------------------------------
/**
* Gets the total size of the map by counting all the values.
*
* @return the total size of the map counting all values
* @since Commons Collections 3.1
*/
public int totalSize() {
int total = 0;
Collection values = super.values();
for (Iterator it = values.iterator(); it.hasNext();) {
Collection coll = (Collection) it.next();
total += coll.size();
}
return total;
}
/**
* Gets the collection mapped to the specified key.
* This method is a convenience method to typecast the result of get(key).
*
* @param key the key to retrieve
* @return the collection mapped to the key, null if no mapping
* @since Commons Collections 3.1
*/
public Collection getCollection(Object key) {
return (Collection) get(key);
}
/**
* Gets the size of the collection mapped to the specified key.
*
* @param key the key to get size for
* @return the size of the collection at the key, zero if key not in map
* @since Commons Collections 3.1
*/
public int size(Object key) {
Collection coll = getCollection(key);
if (coll == null) {
return 0;
}
return coll.size();
}
/**
* Gets an iterator for the collection mapped to the specified key.
*
* @param key the key to get an iterator for
* @return the iterator of the collection at the key, empty iterator if key not in map
* @since Commons Collections 3.1
*/
public Iterator iterator(Object key) {
Collection coll = getCollection(key);
if (coll == null) {
return EmptyIterator.INSTANCE;
}
return coll.iterator();
}
/**
* Adds the value to the collection associated with the specified key.
*
* Unlike a normal Map the previous value is not replaced.
* Instead the new value is added to the collection stored against the key.
*
* @param key the key to store against
* @param value the value to add to the collection at the key
* @return the value added if the map changed and null if the map did not change
*/
public Object put(Object key, Object value) {
// NOTE:: put is called during deserialization in JDK < 1.4 !!!!!!
// so we must have a readObject()
Collection coll = getCollection(key);
if (coll == null) {
coll = createCollection(null);
super.put(key, coll);
}
boolean results = coll.add(value);
return (results ? value : null);
}
/**
* Override superclass to ensure that MultiMap instances are
* correctly handled.
*
* NOTE: Prior to version 3.2, putAll(map) did not work properly
* when passed a MultiMap.
*
* @param map the map to copy (either a normal or multi map)
*/
public void putAll(Map map) {
if (map instanceof MultiMap) {
for (Iterator it = map.entrySet().iterator(); it.hasNext();) {
Map.Entry entry = (Map.Entry) it.next();
Collection coll = (Collection) entry.getValue();
putAll(entry.getKey(), coll);
}
} else {
for (Iterator it = map.entrySet().iterator(); it.hasNext();) {
Map.Entry entry = (Map.Entry) it.next();
put(entry.getKey(), entry.getValue());
}
}
}
/**
* Adds a collection of values to the collection associated with the specified key.
*
* @param key the key to store against
* @param values the values to add to the collection at the key, null ignored
* @return true if this map changed
* @since Commons Collections 3.1
*/
public boolean putAll(Object key, Collection values) {
if (values == null || values.size() == 0) {
return false;
}
Collection coll = getCollection(key);
if (coll == null) {
coll = createCollection(values);
if (coll.size() == 0) {
return false;
}
super.put(key, coll);
return true;
} else {
return coll.addAll(values);
}
}
/**
* Checks whether the map contains the value specified.
*
* This checks all collections against all keys for the value, and thus could be slow.
*
* @param value the value to search for
* @return true if the map contains the value
*/
public boolean containsValue(Object value) {
Set pairs = super.entrySet();
if (pairs == null) {
return false;
}
Iterator pairsIterator = pairs.iterator();
while (pairsIterator.hasNext()) {
Map.Entry keyValuePair = (Map.Entry) pairsIterator.next();
Collection coll = (Collection) keyValuePair.getValue();
if (coll.contains(value)) {
return true;
}
}
return false;
}
/**
* Checks whether the collection at the specified key contains the value.
*
* @param value the value to search for
* @return true if the map contains the value
* @since Commons Collections 3.1
*/
public boolean containsValue(Object key, Object value) {
Collection coll = getCollection(key);
if (coll == null) {
return false;
}
return coll.contains(value);
}
/**
* Removes a specific value from map.
*
* The item is removed from the collection mapped to the specified key.
* Other values attached to that key are unaffected.
*
* If the last value for a key is removed, null will be returned
* from a subsequant get(key).
*
* @param key the key to remove from
* @param item the value to remove
* @return the value removed (which was passed in), null if nothing removed
*/
public Object remove(Object key, Object item) {
Collection valuesForKey = getCollection(key);
if (valuesForKey == null) {
return null;
}
boolean removed = valuesForKey.remove(item);
if (removed == false) {
return null;
}
// remove the list if it is now empty
// (saves space, and allows equals to work)
if (valuesForKey.isEmpty()){
remove(key);
}
return item;
}
/**
* Clear the map.
*
* This clears each collection in the map, and so may be slow.
*/
public void clear() {
// For gc, clear each list in the map
Set pairs = super.entrySet();
Iterator pairsIterator = pairs.iterator();
while (pairsIterator.hasNext()) {
Map.Entry keyValuePair = (Map.Entry) pairsIterator.next();
Collection coll = (Collection) keyValuePair.getValue();
coll.clear();
}
super.clear();
}
/**
* Gets a collection containing all the values in the map.
*
* This returns a collection containing the combination of values from all keys.
*
* @return a collection view of the values contained in this map
*/
public Collection values() {
Collection vs = values;
return (vs != null ? vs : (values = new Values()));
}
/**
* Gets the values iterator from the superclass, as used by inner class.
*
* @return iterator
*/
Iterator superValuesIterator() {
return super.values().iterator();
}
//-----------------------------------------------------------------------
/**
* Inner class to view the elements.
*/
private class Values extends AbstractCollection {
public Iterator iterator() {
return new ValueIterator();
}
public int size() {
int compt = 0;
Iterator it = iterator();
while (it.hasNext()) {
it.next();
compt++;
}
return compt;
}
public void clear() {
MultiHashMap.this.clear();
}
}
/**
* Inner iterator to view the elements.
*/
private class ValueIterator implements Iterator {
private Iterator backedIterator;
private Iterator tempIterator;
private ValueIterator() {
backedIterator = MultiHashMap.this.superValuesIterator();
}
private boolean searchNextIterator() {
while (tempIterator == null || tempIterator.hasNext() == false) {
if (backedIterator.hasNext() == false) {
return false;
}
tempIterator = ((Collection) backedIterator.next()).iterator();
}
return true;
}
public boolean hasNext() {
return searchNextIterator();
}
public Object next() {
if (searchNextIterator() == false) {
throw new NoSuchElementException();
}
return tempIterator.next();
}
public void remove() {
if (tempIterator == null) {
throw new IllegalStateException();
}
tempIterator.remove();
}
}
//-----------------------------------------------------------------------
/**
* Clones the map creating an independent copy.
*
* The clone will shallow clone the collections as well as the map.
*
* @return the cloned map
*/
public Object clone() {
MultiHashMap cloned = (MultiHashMap) super.clone();
// clone each Collection container
for (Iterator it = cloned.entrySet().iterator(); it.hasNext();) {
Map.Entry entry = (Map.Entry) it.next();
Collection coll = (Collection) entry.getValue();
Collection newColl = createCollection(coll);
entry.setValue(newColl);
}
return cloned;
}
/**
* Creates a new instance of the map value Collection container.
*
* This method can be overridden to use your own collection type.
*
* @param coll the collection to copy, may be null
* @return the new collection
*/
protected Collection createCollection(Collection coll) {
if (coll == null) {
return new ArrayList();
} else {
return new ArrayList(coll);
}
}
}