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Generic Evolver utility classes

There is a newer version: 3.5.0

package fi.evolver.utils.collection;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.Optional;

public class CollectionUtils {

	private CollectionUtils() { }


	/**
	 * Null safe method for getting the first element of a list.
	 *
	 * @param list The list.
	 * @return The first element of the list if available.
	 */
	public static  Optional first(List list) {
		return Optional.ofNullable(list)
				.filter(l -> !l.isEmpty())
				.map(l -> l.get(0));
	}


	/**
	 * Null safe method for getting the last element of a list.
	 *
	 * @param list The list.
	 * @return The last element of the list if available.
	 */
	public static  Optional last(List list) {
		return Optional.ofNullable(list)
				.filter(l -> !l.isEmpty())
				.map(l -> l.get(l.size() - 1));
	}

	public static boolean isNullOrEmpty(Collection collection) {
		return collection == null || collection.isEmpty();
	}

	/**
	 * Null-safe way to check if a collection contains elements.
	 * @param collection the collection to check
	 * @return true if the collection contains elements, false if it is null or empty
	 */
	public static boolean hasElements(Collection collection) {
		return !isNullOrEmpty(collection);
	}

	/**
	 * Creates a list with the elements of the first parameter in iteration order except for any elements found in the
	 * second parameter.
	 */
	public static  List minus(List original, Collection excluded) {
		List result = new ArrayList<>(original);
		result.removeAll(excluded);
		return result;
	}

}