1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 package org.apache.commons.collections4; 18 19 /** 20 * Marker interface for collections, maps and iterators that are unmodifiable. 21 * <p> 22 * This interface enables testing such as: 23 * </p> 24 * <pre> 25 * if (coll instanceof Unmodifiable) { 26 * coll = new ArrayList(coll); 27 * } 28 * // now we know coll is modifiable 29 * </pre> 30 * <p> 31 * Of course all this only works if you use the Unmodifiable classes defined 32 * in this library. If you use the JDK unmodifiable class via {@code java.util Collections} 33 * then the interface won't be there. 34 * </p> 35 * 36 * @since 3.0 37 */ 38 public interface Unmodifiable { 39 // marker interface - no methods to implement 40 }