/*
* Copyright 2002-2013 the original author or authors.
*
* Licensed 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.springframework.core;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.NavigableMap;
import java.util.NavigableSet;
import java.util.Set;
import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.TreeSet;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
/**
* Factory for collections, being aware of Java 5 and Java 6 collections.
* Mainly for internal use within the framework.
*
* <p>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 final Set<Class<?>> approximableCollectionTypes = new HashSet<Class<?>>(10);
private static final Set<Class<?>> approximableMapTypes = new HashSet<Class<?>>(6);
static {
// Standard collection interfaces
approximableCollectionTypes.add(Collection.class);
approximableCollectionTypes.add(List.class);
approximableCollectionTypes.add(Set.class);
approximableCollectionTypes.add(SortedSet.class);
approximableCollectionTypes.add(NavigableSet.class);
approximableMapTypes.add(Map.class);
approximableMapTypes.add(SortedMap.class);
approximableMapTypes.add(NavigableMap.class);
// 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);
}
/**
* 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 {@code true} if the type is approximable,
* {@code 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.
* <p>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 <E> Collection<E> createApproximateCollection(Object collection, int initialCapacity) {
if (collection instanceof LinkedList) {
return new LinkedList<E>();
}
else if (collection instanceof List) {
return new ArrayList<E>(initialCapacity);
}
else if (collection instanceof SortedSet) {
return new TreeSet<E>(((SortedSet<E>) collection).comparator());
}
else {
return new LinkedHashSet<E>(initialCapacity);
}
}
/**
* Create the most appropriate collection for the given collection type.
* <p>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
*/
@SuppressWarnings("unchecked")
public static <E> Collection<E> createCollection(Class<?> collectionType, int initialCapacity) {
if (collectionType.isInterface()) {
if (List.class.equals(collectionType)) {
return new ArrayList<E>(initialCapacity);
}
else if (SortedSet.class.equals(collectionType) || NavigableSet.class.equals(collectionType)) {
return new TreeSet<E>();
}
else if (Set.class.equals(collectionType) || Collection.class.equals(collectionType)) {
return new LinkedHashSet<E>(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<E>) collectionType.newInstance();
}
catch (Exception ex) {
throw new IllegalArgumentException("Could not instantiate Collection type: " +
collectionType.getName(), ex);
}
}
}
/**
* 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 {@code true} if the type is approximable,
* {@code 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.
* <p>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 <K, V> Map<K, V> createApproximateMap(Object map, int initialCapacity) {
if (map instanceof SortedMap) {
return new TreeMap<K, V>(((SortedMap<K, V>) map).comparator());
}
else {
return new LinkedHashMap<K, V>(initialCapacity);
}
}
/**
* Create the most approximate map for the given map.
* <p>Creates a TreeMap or linked Map for a SortedMap or Map, respectively.
* @param mapType 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
*/
@SuppressWarnings({ "unchecked", "rawtypes" })
public static <K, V> Map<K, V> createMap(Class<?> mapType, int initialCapacity) {
if (mapType.isInterface()) {
if (Map.class.equals(mapType)) {
return new LinkedHashMap<K, V>(initialCapacity);
}
else if (SortedMap.class.equals(mapType) || NavigableMap.class.equals(mapType)) {
return new TreeMap<K, V>();
}
else if (MultiValueMap.class.equals(mapType)) {
return new LinkedMultiValueMap();
}
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<K, V>) mapType.newInstance();
}
catch (Exception ex) {
throw new IllegalArgumentException("Could not instantiate Map type: " +
mapType.getName(), ex);
}
}
}
}