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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  
18  package org.apache.commons.lang3.mutable;
19  
20  /**
21   * Provides mutable access to a value.
22   * <p>
23   * <code>Mutable</code> is used as a generic interface to the implementations in this package.
24   * <p>
25   * A typical use case would be to enable a primitive or string to be passed to a method and allow that method to
26   * effectively change the value of the primitive/string. Another use case is to store a frequently changing primitive in
27   * a collection (for example a total in a map) without needing to create new Integer/Long wrapper objects.
28   * 
29   * @param <T> the type to set and get 
30   * @since 2.1
31   * @version $Id: Mutable.java 1478488 2013-05-02 19:05:44Z ggregory $
32   */
33  public interface Mutable<T> {
34  
35      /**
36       * Gets the value of this mutable.
37       * 
38       * @return the stored value
39       */
40      T getValue();
41  
42      /**
43       * Sets the value of this mutable.
44       * 
45       * @param value
46       *            the value to store
47       * @throws NullPointerException
48       *             if the object is null and null is invalid
49       * @throws ClassCastException
50       *             if the type is invalid
51       */
52      void setValue(T value);
53  
54  }