Marker interface for unmodifiable collections/maps/iterators/pairs

git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/collections/trunk@131314 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/commons/collections/Unmodifiable.java

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+/*
+ * $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/java/org/apache/commons/collections/Unmodifiable.java,v 1.1 2003/11/02 17:05:50 scolebourne Exp $
+ * ====================================================================
+ *
+ * The Apache Software License, Version 1.1
+ *
+ * Copyright (c) 2001-2003 The Apache Software Foundation.  All rights
+ * reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
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+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. The end-user documentation included with the redistribution, if
+ *    any, must include the following acknowledgement:
+ *       "This product includes software developed by the
+ *        Apache Software Foundation (http://www.apache.org/)."
+ *    Alternately, this acknowledgement may appear in the software itself,
+ *    if and wherever such third-party acknowledgements normally appear.
+ *
+ * 4. The names "The Jakarta Project", "Commons", and "Apache Software
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+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation.  For more
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+ *
+ */
+package org.apache.commons.collections;
+
+/**
+ * Marker interface for collections, maps and iterators that are unmodifiable.
+ * <p>
+ * This interface enables testing such as:
+ * <pre>
+ * if (coll instanceof Unmodifiable) {
+ *   coll = new ArrayList(coll);
+ * }
+ * // now we know coll is modifiable
+ * </pre>
+ * Of course all this only works if you use the Unmodifiable classes defined
+ * in this library. If you use the JDK unmodifiable class via java util Collections
+ * then the interface won't be there.
+ *  
+ * @since Commons Collections 3.0
+ * @version $Revision: 1.1 $ $Date: 2003/11/02 17:05:50 $
+ *
+ * @author Stephen Colebourne
+ */
+public interface Unmodifiable {
+    // marker interface
+}