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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   * {@link Mutable} is used as a generic interface to the implementations in this package.
24   * </p>
25   * <p>
26   * A typical use case would be to enable a primitive or string to be passed to a method and allow that method to
27   * effectively change the value of the primitive/string. Another use case is to store a frequently changing primitive in
28   * a collection (for example a total in a map) without needing to create new Integer/Long wrapper objects.
29   * </p>
30   *
31   * @param <T> the type to set and get
32   * @since 2.1
33   */
34  public interface Mutable<T> {
35  
36      /**
37       * Gets the value of this mutable.
38       *
39       * @return the stored value
40       */
41      T getValue();
42  
43      /**
44       * Sets the value of this mutable.
45       *
46       * @param value
47       *            the value to store
48       * @throws NullPointerException
49       *             if the object is null and null is invalid
50       * @throws ClassCastException
51       *             if the type is invalid
52       */
53      void setValue(T value);
54  
55  }