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Common components used throughout the Release process.

There is a newer version: 1.2.2

package org.reactome.util.general;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Optional;
import java.util.Set;

/**
 * This class provides helper methods for manipulation of collection data
 * @author jweiser
 */
public class CollectionUtils {

	/**
	 * Returns a list with the elements in the passed collection or an empty list if the passed collection is
	 * null.  This method is meant to guard against null values to eliminate the need for conditionals checking
	 * for null and to allow uses such as iteration in loops directly.
	 * @param  Type of the elements for the passed collection and returned list
	 * @param collection Collection of type E
	 * @return List of type E with the elements in the collection or an empty List of type E if the collection is null
	 */
	public static  List safeList(Collection collection) {
		return Optional.ofNullable(collection).map(CollectionUtils::convertToList).orElse(Collections.emptyList());
	}

	/**
	 * Returns a set with the elements in the passed collection or an empty set if the passed collection is
	 * null.  This method is meant to guard against null values to eliminate the need for conditionals checking
	 * for null and to allow uses such as iteration in loops directly.
	 * @param  Type of the elements for the passed collection and returned set
	 * @param collection Collection of type E
	 * @return Set of type E with the elements in the collection or an empty Set of type E if the collection is null
	 */
	public static  Set safeSet(Collection collection) {
		return Optional.ofNullable(collection).map(CollectionUtils::convertToSet).orElse(Collections.emptySet());
	}

	/**
	 * Returns a list with all the elements of the passed lists in the order the lists are received (i.e. flattens
	 * multiple lists into one).
	 * @param  Type of the elements for the passed lists and returned list
	 * @param lists List objects of type E to be combined into a single list
	 * @return Combined list of type E or an empty List of type E if the lists received are null or empty
	 */
	@SafeVarargs
	public static  List combineLists(List ...lists) {
		List combinedList = new ArrayList<>();

		for (List list : lists) {
			if (list != null) {
				combinedList.addAll(list);
			}
		}

		return combinedList;
	}

	private static  List convertToList(Collection collection) {
		return new ArrayList<>(collection);
	}

	private static  Set convertToSet(Collection collection) {
		return new HashSet<>(collection);
	}
}