org.tinygroup.commons.tools.CollectionFactory Maven / Gradle / Ivy
/**
* Copyright (c) 1997-2013, www.tinygroup.org ([email protected]).
*
* Licensed under the GPL, Version 3.0 (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.gnu.org/licenses/gpl.html
*
* 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.tinygroup.commons.tools;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.CopyOnWriteArraySet;
/**
* Factory for collections, being aware of Java 5 and Java 6 collections.
* Mainly for internal use within the framework.
*
* The goal of this class is to avoid runtime dependencies on a specific
* Java version, while nevertheless using the best collection implementation
* that is available at runtime.
*
* @author Juergen Hoeller
* @author Arjen Poutsma
* @since 1.1.1
*/
public abstract class CollectionFactory {
private static Class navigableSetClass = null;
private static Class navigableMapClass = null;
private static final Set approximableCollectionTypes = new HashSet(10);
private static final Set approximableMapTypes = new HashSet(6);
static {
// Standard collection interfaces
approximableCollectionTypes.add(Collection.class);
approximableCollectionTypes.add(List.class);
approximableCollectionTypes.add(Set.class);
approximableCollectionTypes.add(SortedSet.class);
approximableMapTypes.add(Map.class);
approximableMapTypes.add(SortedMap.class);
// New Java 6 collection interfaces
ClassLoader cl = CollectionFactory.class.getClassLoader();
try {
navigableSetClass = cl.loadClass("java.util.NavigableSet");
navigableMapClass = cl.loadClass("java.util.NavigableMap");
approximableCollectionTypes.add(navigableSetClass);
approximableMapTypes.add(navigableMapClass);
}
catch (ClassNotFoundException ex) {
// not running on Java 6 or above...
}
// Common concrete collection classes
approximableCollectionTypes.add(ArrayList.class);
approximableCollectionTypes.add(LinkedList.class);
approximableCollectionTypes.add(HashSet.class);
approximableCollectionTypes.add(LinkedHashSet.class);
approximableCollectionTypes.add(TreeSet.class);
approximableMapTypes.add(HashMap.class);
approximableMapTypes.add(LinkedHashMap.class);
approximableMapTypes.add(TreeMap.class);
}
/**
* Create a linked Set if possible: This implementation always
* creates a {@link java.util.LinkedHashSet}, since Spring 2.5
* requires JDK 1.4 anyway.
* @param initialCapacity the initial capacity of the Set
* @return the new Set instance
* @deprecated as of Spring 2.5, for usage on JDK 1.4 or higher
*/
@Deprecated
public static Set createLinkedSetIfPossible(int initialCapacity) {
return new LinkedHashSet(initialCapacity);
}
/**
* Create a copy-on-write Set (allowing for synchronization-less iteration) if possible:
* This implementation always creates a {@link java.util.concurrent.CopyOnWriteArraySet},
* since Spring 3 requires JDK 1.5 anyway.
* @return the new Set instance
* @deprecated as of Spring 3.0, for usage on JDK 1.5 or higher
*/
@Deprecated
public static Set createCopyOnWriteSet() {
return new CopyOnWriteArraySet();
}
/**
* Create a linked Map if possible: This implementation always
* creates a {@link java.util.LinkedHashMap}, since Spring 2.5
* requires JDK 1.4 anyway.
* @param initialCapacity the initial capacity of the Map
* @return the new Map instance
* @deprecated as of Spring 2.5, for usage on JDK 1.4 or higher
*/
@Deprecated
public static Map createLinkedMapIfPossible(int initialCapacity) {
return new LinkedHashMap(initialCapacity);
}
/**
* Create an identity Map if possible: This implementation always
* creates a {@link java.util.IdentityHashMap}, since Spring 2.5
* requires JDK 1.4 anyway.
* @param initialCapacity the initial capacity of the Map
* @return the new Map instance
* @deprecated as of Spring 2.5, for usage on JDK 1.4 or higher
*/
@Deprecated
public static Map createIdentityMapIfPossible(int initialCapacity) {
return new IdentityHashMap(initialCapacity);
}
/**
* Create a concurrent Map if possible: This implementation always
* creates a {@link java.util.concurrent.ConcurrentHashMap}, since Spring 3.0
* requires JDK 1.5 anyway.
* @param initialCapacity the initial capacity of the Map
* @return the new Map instance
* @deprecated as of Spring 3.0, for usage on JDK 1.5 or higher
*/
@Deprecated
public static Map createConcurrentMapIfPossible(int initialCapacity) {
return new ConcurrentHashMap(initialCapacity);
}
/**
* Create a concurrent Map with a dedicated {@link ConcurrentMap} interface:
* This implementation always creates a {@link java.util.concurrent.ConcurrentHashMap},
* since Spring 3.0 requires JDK 1.5 anyway.
* @param initialCapacity the initial capacity of the Map
* @return the new ConcurrentMap instance
* @deprecated as of Spring 3.0, for usage on JDK 1.5 or higher
*/
@Deprecated
public static ConcurrentMap createConcurrentMap(int initialCapacity) {
return new JdkConcurrentHashMap(initialCapacity);
}
/**
* Determine whether the given collection type is an approximable type,
* i.e. a type that {@link #createApproximateCollection} can approximate.
* @param collectionType the collection type to check
* @return true if the type is approximable,
* false if it is not
*/
public static boolean isApproximableCollectionType(Class collectionType) {
return (collectionType != null && approximableCollectionTypes.contains(collectionType));
}
/**
* Create the most approximate collection for the given collection.
* Creates an ArrayList, TreeSet or linked Set for a List, SortedSet
* or Set, respectively.
* @param collection the original Collection object
* @param initialCapacity the initial capacity
* @return the new Collection instance
* @see java.util.ArrayList
* @see java.util.TreeSet
* @see java.util.LinkedHashSet
*/
@SuppressWarnings("unchecked")
public static Collection createApproximateCollection(Object collection, int initialCapacity) {
if (collection instanceof LinkedList) {
return new LinkedList();
}
else if (collection instanceof List) {
return new ArrayList(initialCapacity);
}
else if (collection instanceof SortedSet) {
return new TreeSet(((SortedSet) collection).comparator());
}
else {
return new LinkedHashSet(initialCapacity);
}
}
/**
* Create the most appropriate collection for the given collection type.
*
Creates an ArrayList, TreeSet or linked Set for a List, SortedSet
* or Set, respectively.
* @param collectionType the desired type of the target Collection
* @param initialCapacity the initial capacity
* @return the new Collection instance
* @see java.util.ArrayList
* @see java.util.TreeSet
* @see java.util.LinkedHashSet
*/
public static Collection createCollection(Class collectionType, int initialCapacity) {
if (collectionType.isInterface()) {
if (List.class.equals(collectionType)) {
return new ArrayList(initialCapacity);
}
else if (SortedSet.class.equals(collectionType) || collectionType.equals(navigableSetClass)) {
return new TreeSet();
}
else if (Set.class.equals(collectionType) || Collection.class.equals(collectionType)) {
return new LinkedHashSet(initialCapacity);
}
else {
throw new IllegalArgumentException("Unsupported Collection interface: " + collectionType.getName());
}
}
else {
if (!Collection.class.isAssignableFrom(collectionType)) {
throw new IllegalArgumentException("Unsupported Collection type: " + collectionType.getName());
}
try {
return (Collection) collectionType.newInstance();
}
catch (Exception ex) {
throw new IllegalArgumentException("Could not instantiate Collection type: " + collectionType.getName());
}
}
}
/**
* Determine whether the given map type is an approximable type,
* i.e. a type that {@link #createApproximateMap} can approximate.
* @param mapType the map type to check
* @return true if the type is approximable,
* false if it is not
*/
public static boolean isApproximableMapType(Class mapType) {
return (mapType != null && approximableMapTypes.contains(mapType));
}
/**
* Create the most approximate map for the given map.
*
Creates a TreeMap or linked Map for a SortedMap or Map, respectively.
* @param map the original Map object
* @param initialCapacity the initial capacity
* @return the new Map instance
* @see java.util.TreeMap
* @see java.util.LinkedHashMap
*/
@SuppressWarnings("unchecked")
public static Map createApproximateMap(Object map, int initialCapacity) {
if (map instanceof SortedMap) {
return new TreeMap(((SortedMap) map).comparator());
}
else {
return new LinkedHashMap(initialCapacity);
}
}
/**
* Create the most approximate map for the given map.
*
Creates a TreeMap or linked Map for a SortedMap or Map, respectively.
* @param collectionType the desired type of the target Map
* @param initialCapacity the initial capacity
* @return the new Map instance
* @see java.util.TreeMap
* @see java.util.LinkedHashMap
*/
public static Map createMap(Class mapType, int initialCapacity) {
if (mapType.isInterface()) {
if (Map.class.equals(mapType)) {
return new LinkedHashMap(initialCapacity);
}
else if (SortedMap.class.equals(mapType) || mapType.equals(navigableMapClass)) {
return new TreeMap();
}
else {
throw new IllegalArgumentException("Unsupported Map interface: " + mapType.getName());
}
}
else {
if (!Map.class.isAssignableFrom(mapType)) {
throw new IllegalArgumentException("Unsupported Map type: " + mapType.getName());
}
try {
return (Map) mapType.newInstance();
}
catch (Exception ex) {
throw new IllegalArgumentException("Could not instantiate Map type: " + mapType.getName());
}
}
}
/**
* ConcurrentMap adapter for the JDK ConcurrentHashMap class.
*/
@Deprecated
private static class JdkConcurrentHashMap extends ConcurrentHashMap implements ConcurrentMap {
private JdkConcurrentHashMap(int initialCapacity) {
super(initialCapacity);
}
}
}