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CollectionFactory.java
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CollectionFactory.java
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/**
* Copyright (C) 2020 Czech Technical University in Prague
* <p>
* This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
* License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later
* version.
* <p>
* This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
* warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
* details. You should have received a copy of the GNU General Public License along with this program. If not, see
* <http://www.gnu.org/licenses/>.
*/
package cz.cvut.kbss.jopa.utils;
import cz.cvut.kbss.jopa.model.metamodel.CollectionType;
import java.util.*;
public final class CollectionFactory {
private CollectionFactory() {
throw new AssertionError();
}
/**
* Creates an instance of a {@link Collection} implementation best matching the specified instance.
* <p>
* E.g. for any kind of {@link List}, an {@link ArrayList} is returned.
*
* @param collection Create matching instance for this collection
* @return Best matching collection instance
*/
public static Collection<?> createInstance(Collection<?> collection) {
Objects.requireNonNull(collection);
if (collection instanceof List) {
return new ArrayList<>(collection.size());
} else if (collection instanceof Set) {
return new HashSet<>(collection.size());
}
throw new IllegalArgumentException("Unsupported collection type: " + collection);
}
/**
* Creates default collection for the specified collection type.
*
* @param collectionType Type of the collection to create
* @return Collection implementation instance
*/
public static <T> Collection<T> createDefaultCollection(CollectionType collectionType) {
switch (collectionType) {
case LIST:
return new ArrayList<>();
case SET:
case COLLECTION: // Intentional fall-through
return new HashSet<>();
default:
throw new IllegalArgumentException("Collection type " + collectionType + " is not supported.");
}
}
/**
* Creates default instance of {@link Map}.
*
* @return Default Map implementation instance
*/
public static Map<Object, Object> createDefaultMap() {
return new HashMap<>();
}
public static CollectionType resolveCollectionType(Class<?> javaType) {
if (List.class.isAssignableFrom(javaType)) {
return CollectionType.LIST;
} else if (Set.class.isAssignableFrom(javaType)) {
return CollectionType.SET;
} else if (Collection.class.isAssignableFrom(javaType)) {
return CollectionType.COLLECTION;
} else if (Map.class.isAssignableFrom(javaType)) {
return CollectionType.MAP;
} else {
throw new IllegalArgumentException();
}
}
}