001/*
002 * nimbus-jose-jwt
003 *
004 * Copyright 2012-2016, Connect2id Ltd and contributors.
005 *
006 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use
007 * this file except in compliance with the License. You may obtain a copy of the
008 * License at
009 *
010 *    http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software distributed
013 * under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
014 * CONDITIONS OF ANY KIND, either express or implied. See the License for the
015 * specific language governing permissions and limitations under the License.
016 */
017
018package com.nimbusds.jose.util;
019
020
021import java.util.HashSet;
022import java.util.Set;
023
024/**
025 * Collection utilities.
026 */
027public class CollectionUtils {
028
029
030        /**
031         * Returns {@code true} if the specified set contains {@code null}.
032         * Prevents a NPE when calling {@code Set.contains(null)} on a
033         * {@code Java 9 Set.of()}.
034         *
035         * @param set The set. Must not be {@code null}.
036         *
037         * @return {@code true} if the set contains {@code null}, else
038         *         {@code false}.
039         */
040        public static <T> boolean containsNull(final Set<T> set) {
041                HashSet<T> defensiveCopy = new HashSet<>(set);
042                return defensiveCopy.contains(null);
043        }
044
045
046        /**
047         * Prevents public instantiation.
048         */
049        private CollectionUtils() {
050        }
051}