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 * Of course all this only works if you use the Unmodifiable classes defined
31 * in this library. If you use the JDK unmodifiable class via {@code java.util Collections}
32 * then the interface won't be there.
33 *
34 * @since 3.0
35 */
36 public interface Unmodifiable {
37 // marker interface - no methods to implement
38 }