Java tutorial
//package com.java2s; /** * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ import java.util.Collection; import java.util.Collections; public class Main { /** * @return <code>coll</code> if it is non-null and non-empty. Otherwise, * returns a list with a single null value. */ private static Collection<String> emptyAsSingletonNull(Collection<String> coll) { if (coll == null || coll.isEmpty()) { return Collections.singletonList(null); } else { return coll; } } }