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      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.collections;
     18 
     19 /**
     20  * Marker interface for collections, maps and iterators that are unmodifiable.
     21  * <p>
     22  * This interface enables testing such as:
     23  * <pre>
     24  * if (coll instanceof Unmodifiable) {
     25  *   coll = new ArrayList(coll);
     26  * }
     27  * // now we know coll is modifiable
     28  * </pre>
     29  * Of course all this only works if you use the Unmodifiable classes defined
     30  * in this library. If you use the JDK unmodifiable class via java util Collections
     31  * then the interface won't be there.
     32  *
     33  * @since Commons Collections 3.0
     34  * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
     35  *
     36  * @author Stephen Colebourne
     37  */
     38 public interface Unmodifiable {
     39     // marker interface - no methods to implement
     40 }
     41