Java tutorial
//package com.java2s; /* * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER. * * Copyright 2011 OpenConcerto, by ILM Informatique. All rights reserved. * * The contents of this file are subject to the terms of the GNU General Public License Version 3 * only ("GPL"). You may not use this file except in compliance with the License. You can obtain a * copy of the License at http://www.gnu.org/licenses/gpl-3.0.html See the License for the specific * language governing permissions and limitations under the License. * * When distributing the software, include this License Header Notice in each file. */ import java.util.Collection; import java.util.List; public class Main { /** * Return the first item of <code>l</code> if it's the only one, otherwise <code>null</code>. * * @param <T> type of list. * @param l the list. * @return the first item of <code>l</code> or <code>null</code>. */ public static <T> T getSole(List<T> l) { return l.size() == 1 ? l.get(0) : null; } public static <T> T getSole(Collection<T> l) { return l.size() == 1 ? l.iterator().next() : null; } }