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diff --git a/src/main/java/org/apache/commons/lang3/mutable/Mutable.java b/src/main/java/org/apache/commons/lang3/mutable/Mutable.java
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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.commons.lang3.mutable;
+
+/**
+ * Provides mutable access to a value.
+ * <p>
+ * {@link Mutable} is used as a generic interface to the implementations in this package.
+ * </p>
+ * <p>
+ * A typical use case would be to enable a primitive or string to be passed to a method and allow that method to
+ * effectively change the value of the primitive/string. Another use case is to store a frequently changing primitive in
+ * a collection (for example a total in a map) without needing to create new Integer/Long wrapper objects.
+ * </p>
+ *
+ * @param <T> the type to set and get
+ * @since 2.1
+ */
+public interface Mutable<T> {
+
+    /**
+     * Gets the value of this mutable.
+     *
+     * @return the stored value
+     */
+    T getValue();
+
+    /**
+     * Sets the value of this mutable.
+     *
+     * @param value
+     *            the value to store
+     * @throws NullPointerException
+     *             if the object is null and null is invalid
+     * @throws ClassCastException
+     *             if the type is invalid
+     */
+    void setValue(T value);
+
+}