Commons Collections example source code file (CompositeMap.java)
The Commons Collections CompositeMap.java source code/*
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* 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.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import org.apache.commons.collections.CollectionUtils;
import org.apache.commons.collections.collection.CompositeCollection;
import org.apache.commons.collections.set.CompositeSet;
/**
* Decorates a map of other maps to provide a single unified view.
* <p>
* Changes made to this map will actually be made on the decorated map.
* Add and remove operations require the use of a pluggable strategy. If no
* strategy is provided then add and remove are unsupported.
* <p>
* <strong>Note that CompositeMap is not synchronized and is not thread-safe.
* If you wish to use this map from multiple threads concurrently, you must use
* appropriate synchronization. The simplest approach is to wrap this map
* using {@link java.util.Collections#synchronizedMap(Map)}. This class may throw
* exceptions when accessed by concurrent threads without synchronization.
*
* @since Commons Collections 3.0
* @version $Revision: 647116 $ $Date: 2008-04-11 12:23:08 +0100 (Fri, 11 Apr 2008) $
*
* @author Brian McCallister
*/
public class CompositeMap implements Map {
/** Array of all maps in the composite */
private Map[] composite;
/** Handle mutation operations */
private MapMutator mutator;
/**
* Create a new, empty, CompositeMap.
*/
public CompositeMap() {
this(new Map[]{}, null);
}
/**
* Create a new CompositeMap with two composited Map instances.
*
* @param one the first Map to be composited
* @param two the second Map to be composited
* @throws IllegalArgumentException if there is a key collision
*/
public CompositeMap(Map one, Map two) {
this(new Map[]{one, two}, null);
}
/**
* Create a new CompositeMap with two composited Map instances.
*
* @param one the first Map to be composited
* @param two the second Map to be composited
* @param mutator MapMutator to be used for mutation operations
*/
public CompositeMap(Map one, Map two, MapMutator mutator) {
this(new Map[]{one, two}, mutator);
}
/**
* Create a new CompositeMap which composites all of the Map instances in the
* argument. It copies the argument array, it does not use it directly.
*
* @param composite the Maps to be composited
* @throws IllegalArgumentException if there is a key collision
*/
public CompositeMap(Map[] composite) {
this(composite, null);
}
/**
* Create a new CompositeMap which composites all of the Map instances in the
* argument. It copies the argument array, it does not use it directly.
*
* @param composite Maps to be composited
* @param mutator MapMutator to be used for mutation operations
*/
public CompositeMap(Map[] composite, MapMutator mutator) {
this.mutator = mutator;
this.composite = new Map[0];
for (int i = composite.length - 1; i >= 0; --i) {
this.addComposited(composite[i]);
}
}
//-----------------------------------------------------------------------
/**
* Specify the MapMutator to be used by mutation operations.
*
* @param mutator the MapMutator to be used for mutation delegation
*/
public void setMutator(MapMutator mutator) {
this.mutator = mutator;
}
/**
* Add an additional Map to the composite.
*
* @param map the Map to be added to the composite
* @throws IllegalArgumentException if there is a key collision and there is no
* MapMutator set to handle it.
*/
public synchronized void addComposited(Map map) throws IllegalArgumentException {
for (int i = composite.length - 1; i >= 0; --i) {
Collection intersect = CollectionUtils.intersection(this.composite[i].keySet(), map.keySet());
if (intersect.size() != 0) {
if (this.mutator == null) {
throw new IllegalArgumentException("Key collision adding Map to CompositeMap");
}
else {
this.mutator.resolveCollision(this, this.composite[i], map, intersect);
}
}
}
Map[] temp = new Map[this.composite.length + 1];
System.arraycopy(this.composite, 0, temp, 0, this.composite.length);
temp[temp.length - 1] = map;
this.composite = temp;
}
/**
* Remove a Map from the composite.
*
* @param map the Map to be removed from the composite
* @return The removed Map or <code>null if map is not in the composite
*/
public synchronized Map removeComposited(Map map) {
int size = this.composite.length;
for (int i = 0; i < size; ++i) {
if (this.composite[i].equals(map)) {
Map[] temp = new Map[size - 1];
System.arraycopy(this.composite, 0, temp, 0, i);
System.arraycopy(this.composite, i + 1, temp, i, size - i - 1);
this.composite = temp;
return map;
}
}
return null;
}
//-----------------------------------------------------------------------
/**
* Calls <code>clear() on all composited Maps.
*
* @throws UnsupportedOperationException if any of the composited Maps do not support clear()
*/
public void clear() {
for (int i = this.composite.length - 1; i >= 0; --i) {
this.composite[i].clear();
}
}
/**
* Returns <tt>true if this map contains a mapping for the specified
* key. More formally, returns <tt>true if and only if
* this map contains at a mapping for a key <tt>k such that
* <tt>(key==null ? k==null : key.equals(k)). (There can be
* at most one such mapping.)
*
* @param key key whose presence in this map is to be tested.
* @return <tt>true if this map contains a mapping for the specified
* key.
*
* @throws ClassCastException if the key is of an inappropriate type for
* this map (optional).
* @throws NullPointerException if the key is <tt>null and this map
* does not not permit <tt>null keys (optional).
*/
public boolean containsKey(Object key) {
for (int i = this.composite.length - 1; i >= 0; --i) {
if (this.composite[i].containsKey(key)) {
return true;
}
}
return false;
}
/**
* Returns <tt>true if this map maps one or more keys to the
* specified value. More formally, returns <tt>true if and only if
* this map contains at least one mapping to a value <tt>v such that
* <tt>(value==null ? v==null : value.equals(v)). This operation
* will probably require time linear in the map size for most
* implementations of the <tt>Map interface.
*
* @param value value whose presence in this map is to be tested.
* @return <tt>true if this map maps one or more keys to the
* specified value.
* @throws ClassCastException if the value is of an inappropriate type for
* this map (optional).
* @throws NullPointerException if the value is <tt>null and this map
* does not not permit <tt>null values (optional).
*/
public boolean containsValue(Object value) {
for (int i = this.composite.length - 1; i >= 0; --i) {
if (this.composite[i].containsValue(value)) {
return true;
}
}
return false;
}
/**
* Returns a set view of the mappings contained in this map. Each element
* in the returned set is a <code>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
* <tt>Iterator.remove, Set.remove, removeAll,
* <tt>retainAll and clear operations. It does not support
* the <tt>add or addAll operations.
* <p>
* This implementation returns a <code>CompositeSet which
* composites the entry sets from all of the composited maps.
*
* @see CompositeSet
* @return a set view of the mappings contained in this map.
*/
public Set entrySet() {
CompositeSet entries = new CompositeSet();
for (int i = this.composite.length - 1; i >= 0; --i) {
entries.addComposited(this.composite[i].entrySet());
}
return entries;
}
/**
* Returns the value to which this map maps the specified key. Returns
* <tt>null if the map contains no mapping for this key. A return
* value of <tt>null does not necessarily indicate that the
* map contains no mapping for the key; it's also possible that the map
* explicitly maps the key to <tt>null. The containsKey
* operation may be used to distinguish these two cases.
*
* <p>More formally, if this map contains a mapping from a key
* <tt>k to a value v such that (key==null ? k==null :
* key.equals(k))</tt>, then this method returns v; otherwise
* it returns <tt>null. (There can be at most one such mapping.)
*
* @param key key whose associated value is to be returned.
* @return the value to which this map maps the specified key, or
* <tt>null if the map contains no mapping for this key.
*
* @throws ClassCastException if the key is of an inappropriate type for
* this map (optional).
* @throws NullPointerException key is <tt>null and this map does not
* not permit <tt>null keys (optional).
*
* @see #containsKey(Object)
*/
public Object get(Object key) {
for (int i = this.composite.length - 1; i >= 0; --i) {
if (this.composite[i].containsKey(key)) {
return this.composite[i].get(key);
}
}
return null;
}
/**
* Returns <tt>true if this map contains no key-value mappings.
*
* @return <tt>true if this map contains no key-value mappings.
*/
public boolean isEmpty() {
for (int i = this.composite.length - 1; i >= 0; --i) {
if (!this.composite[i].isEmpty()) {
return false;
}
}
return true;
}
/**
* 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 <tt>Iterator.remove, Set.remove,
* <tt>removeAll retainAll, and clear operations.
* It does not support the add or <tt>addAll operations.
* <p>
* This implementation returns a <code>CompositeSet which
* composites the key sets from all of the composited maps.
*
* @return a set view of the keys contained in this map.
*/
public Set keySet() {
CompositeSet keys = new CompositeSet();
for (int i = this.composite.length - 1; i >= 0; --i) {
keys.addComposited(this.composite[i].keySet());
}
return keys;
}
/**
* Associates the specified value with the specified key in this map
* (optional operation). If the map previously contained a mapping for
* this key, the old value is replaced by the specified value. (A map
* <tt>m is said to contain a mapping for a key k if and only
* if {@link #containsKey(Object) m.containsKey(k)} would return
* <tt>true.))
*
* @param key key with which the specified value is to be associated.
* @param value value to be associated with the specified key.
* @return previous value associated with specified key, or <tt>null
* if there was no mapping for key. A <tt>null return can
* also indicate that the map previously associated <tt>null
* with the specified key, if the implementation supports
* <tt>null values.
*
* @throws UnsupportedOperationException if no MapMutator has been specified
* @throws ClassCastException if the class of the specified key or value
* prevents it from being stored in this map.
* @throws IllegalArgumentException if some aspect of this key or value
* prevents it from being stored in this map.
* @throws NullPointerException this map does not permit <tt>null
* keys or values, and the specified key or value is
* <tt>null.
*/
public Object put(Object key, Object value) {
if (this.mutator == null) {
throw new UnsupportedOperationException("No mutator specified");
}
return this.mutator.put(this, this.composite, key, value);
}
/**
* Copies all of the mappings from the specified map to this map
* (optional operation). The effect of this call is equivalent to that
* of calling {@link #put(Object,Object) put(k, v)} on this map once
* for each mapping from key <tt>k to value v in the
* specified map. The behavior of this operation is unspecified if the
* specified map is modified while the operation is in progress.
*
* @param map Mappings to be stored in this map.
*
* @throws UnsupportedOperationException if the <tt>putAll method is
* not supported by this map.
*
* @throws ClassCastException if the class of a key or value in the
* specified map prevents it from being stored in this map.
*
* @throws IllegalArgumentException some aspect of a key or value in the
* specified map prevents it from being stored in this map.
* @throws NullPointerException the specified map is <tt>null, or if
* this map does not permit <tt>null keys or values, and the
* specified map contains <tt>null keys or values.
*/
public void putAll(Map map) {
if (this.mutator == null) {
throw new UnsupportedOperationException("No mutator specified");
}
this.mutator.putAll(this, this.composite, map);
}
/**
* Removes the mapping for this key from this map if it is present
* (optional operation). More formally, if this map contains a mapping
* from key <tt>k to value v such that
* <code>(key==null ? k==null : key.equals(k)), that mapping
* is removed. (The map can contain at most one such mapping.)
*
* <p>Returns the value to which the map previously associated the key, or
* <tt>null if the map contained no mapping for this key. (A
* <tt>null return can also indicate that the map previously
* associated <tt>null with the specified key if the implementation
* supports <tt>null values.) The map will not contain a mapping for
* the specified key once the call returns.
*
* @param key key whose mapping is to be removed from the map.
* @return previous value associated with specified key, or <tt>null
* if there was no mapping for key.
*
* @throws ClassCastException if the key is of an inappropriate type for
* the composited map (optional).
* @throws NullPointerException if the key is <tt>null and the composited map
* does not not permit <tt>null keys (optional).
* @throws UnsupportedOperationException if the <tt>remove method is
* not supported by the composited map containing the key
*/
public Object remove(Object key) {
for (int i = this.composite.length - 1; i >= 0; --i) {
if (this.composite[i].containsKey(key)) {
return this.composite[i].remove(key);
}
}
return null;
}
/**
* Returns the number of key-value mappings in this map. If the
* map contains more than <tt>Integer.MAX_VALUE elements, returns
* <tt>Integer.MAX_VALUE.
*
* @return the number of key-value mappings in this map.
*/
public int size() {
int size = 0;
for (int i = this.composite.length - 1; i >= 0; --i) {
size += this.composite[i].size();
}
return size;
}
/**
* 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
* <tt>Iterator.remove, Collection.remove,
* <tt>removeAll, retainAll and clear operations.
* It does not support the add or <tt>addAll operations.
*
* @return a collection view of the values contained in this map.
*/
public Collection values() {
CompositeCollection keys = new CompositeCollection();
for (int i = this.composite.length - 1; i >= 0; --i) {
keys.addComposited(this.composite[i].values());
}
return keys;
}
/**
* Checks if this Map equals another as per the Map specification.
*
* @param obj the object to compare to
* @return true if the maps are equal
*/
public boolean equals(Object obj) {
if (obj instanceof Map) {
Map map = (Map) obj;
return (this.entrySet().equals(map.entrySet()));
}
return false;
}
/**
* Gets a hash code for the Map as per the Map specification.
*/
public int hashCode() {
int code = 0;
for (Iterator i = this.entrySet().iterator(); i.hasNext();) {
code += i.next().hashCode();
}
return code;
}
/**
* This interface allows definition for all of the indeterminate
* mutators in a CompositeMap, as well as providing a hook for
* callbacks on key collisions.
*/
public static interface MapMutator {
/**
* Called when adding a new Composited Map results in a
* key collision.
*
* @param composite the CompositeMap with the collision
* @param existing the Map already in the composite which contains the
* offending key
* @param added the Map being added
* @param intersect the intersection of the keysets of the existing and added maps
*/
public void resolveCollision(
CompositeMap composite, Map existing, Map added, Collection intersect);
/**
* Called when the CompositeMap.put() method is invoked.
*
* @param map the CompositeMap which is being modified
* @param composited array of Maps in the CompositeMap being modified
* @param key key with which the specified value is to be associated.
* @param value value to be associated with the specified key.
* @return previous value associated with specified key, or <tt>null
* if there was no mapping for key. A <tt>null return can
* also indicate that the map previously associated <tt>null
* with the specified key, if the implementation supports
* <tt>null values.
*
* @throws UnsupportedOperationException if not defined
* @throws ClassCastException if the class of the specified key or value
* prevents it from being stored in this map.
* @throws IllegalArgumentException if some aspect of this key or value
* prevents it from being stored in this map.
* @throws NullPointerException this map does not permit <tt>null
* keys or values, and the specified key or value is
* <tt>null.
*/
public Object put(CompositeMap map, Map[] composited, Object key, Object value);
/**
* Called when the CompositeMap.putAll() method is invoked.
*
* @param map the CompositeMap which is being modified
* @param composited array of Maps in the CompositeMap being modified
* @param mapToAdd Mappings to be stored in this CompositeMap
*
* @throws UnsupportedOperationException if not defined
* @throws ClassCastException if the class of the specified key or value
* prevents it from being stored in this map.
* @throws IllegalArgumentException if some aspect of this key or value
* prevents it from being stored in this map.
* @throws NullPointerException this map does not permit <tt>null
* keys or values, and the specified key or value is
* <tt>null.
*/
public void putAll(CompositeMap map, Map[] composited, Map mapToAdd);
}
}
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