Java tutorial
//package com.java2s; /* * * This file is part of the XiPKI project. * Copyright (c) 2014 - 2015 Lijun Liao * Author: Lijun Liao * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU Affero General Public License version 3 * as published by the Free Software Foundation with the addition of the * following permission added to Section 15 as permitted in Section 7(a): * FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY * THE AUTHOR LIJUN LIAO. LIJUN LIAO DISCLAIMS THE WARRANTY OF NON INFRINGEMENT * OF THIRD PARTY RIGHTS. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU Affero General Public License for more details. * * You should have received a copy of the GNU Affero General Public License * along with this program. If not, see <http://www.gnu.org/licenses/>. * * The interactive user interfaces in modified source and object code versions * of this program must display Appropriate Legal Notices, as required under * Section 5 of the GNU Affero General Public License. * * You can be released from the requirements of the license by purchasing * a commercial license. Buying such a license is mandatory as soon as you * develop commercial activities involving the XiPKI software without * disclosing the source code of your own applications. * * For more information, please contact Lijun Liao at this * address: lijun.liao@gmail.com */ import java.util.Collection; import java.util.Collections; import java.util.HashMap; import java.util.Map; public class Main { public static <K, V> Map<K, V> unmodifiableMap(final Map<? extends K, ? extends V> m) { if (m == null) { return null; } return Collections.unmodifiableMap(m); } public static <K, V> Map<K, V> unmodifiableMap(final Map<? extends K, ? extends V> m, final boolean newMap, final boolean emptyAsNull) { if (m == null) { return null; } if (emptyAsNull && m.isEmpty()) { return null; } return Collections.unmodifiableMap(newMap ? new HashMap<>(m) : m); } public static boolean isEmpty(final Collection<?> c) { return c == null || c.isEmpty(); } public static boolean isEmpty(final Map<?, ?> m) { return m == null || m.isEmpty(); } }