001/*-
002 * #%L
003 * HAPI FHIR JPA Server
004 * %%
005 * Copyright (C) 2014 - 2024 Smile CDR, Inc.
006 * %%
007 * Licensed under the Apache License, Version 2.0 (the "License");
008 * you may not use this file except in compliance with the License.
009 * You may obtain a copy of the License at
010 *
011 *      http://www.apache.org/licenses/LICENSE-2.0
012 *
013 * Unless required by applicable law or agreed to in writing, software
014 * distributed under the License is distributed on an "AS IS" BASIS,
015 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
016 * See the License for the specific language governing permissions and
017 * limitations under the License.
018 * #L%
019 */
020package ca.uhn.fhir.jpa.util;
021
022import java.util.List;
023
024/**
025 * Utility class for working with cartesian products - Use Guava's
026 * {@link com.google.common.collect.Lists#cartesianProduct(List)} method
027 * to actually calculate the product.
028 */
029public class CartesianProductUtil {
030
031        /**
032         * Non instantiable
033         */
034        private CartesianProductUtil() {
035                // nothing
036        }
037
038        /**
039         * Returns the size of the cartesian product
040         *
041         * @throws ArithmeticException If size exceeds {@link Integer#MAX_VALUE}
042         * @since 7.4.0
043         */
044        public static <T> int calculateCartesianProductSize(List<List<T>> theLists) throws ArithmeticException {
045                int retVal = !theLists.isEmpty() ? 1 : 0;
046                for (List<T> theList : theLists) {
047                        retVal = Math.multiplyExact(retVal, theList.size());
048                }
049                return retVal;
050        }
051}