Java tutorial
//package com.java2s; /* * Copyright (c) 2013, OpenCloudDB/MyCAT and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software;Designed and Developed mainly by many Chinese * opensource volunteers. you can redistribute it and/or modify it under the * terms of the GNU General Public License version 2 only, as published by the * Free Software Foundation. * * This code 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 General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Any questions about this component can be directed to it's project Web address * https://code.google.com/p/opencloudb/. * */ import java.util.Collection; import java.util.Collections; import java.util.HashSet; import java.util.Map; import java.util.Set; public class Main { /** * @param orig * if null, return intersect */ public static Set<? extends Object> intersectSet(Set<? extends Object> orig, Set<? extends Object> intersect) { if (orig == null) return intersect; if (intersect == null || orig.isEmpty()) return Collections.emptySet(); Set<Object> set = new HashSet<Object>(orig.size()); for (Object p : orig) { if (intersect.contains(p)) set.add(p); } return set; } public static boolean isEmpty(Collection<?> collection) { return collection == null || collection.isEmpty(); } public static boolean isEmpty(Map<?, ?> map) { return map == null || map.isEmpty(); } }