001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.commons.collections4; 018 019/** 020 * Marker interface for collections, maps and iterators that are unmodifiable. 021 * <p> 022 * This interface enables testing such as: 023 * </p> 024 * <pre> 025 * if (coll instanceof Unmodifiable) { 026 * coll = new ArrayList(coll); 027 * } 028 * // now we know coll is modifiable 029 * </pre> 030 * Of course all this only works if you use the Unmodifiable classes defined 031 * in this library. If you use the JDK unmodifiable class via {@code java.util Collections} 032 * then the interface won't be there. 033 * 034 * @since 3.0 035 */ 036public interface Unmodifiable { 037 // marker interface - no methods to implement 038}