001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 * 
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 * 
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018package org.apache.commons.lang3.mutable;
019
020/**
021 * Provides mutable access to a value.
022 * <p>
023 * <code>Mutable</code> is used as a generic interface to the implementations in this package.
024 * <p>
025 * A typical use case would be to enable a primitive or string to be passed to a method and allow that method to
026 * effectively change the value of the primitive/string. Another use case is to store a frequently changing primitive in
027 * a collection (for example a total in a map) without needing to create new Integer/Long wrapper objects.
028 * 
029 * @param <T> the type to set and get 
030 * @since 2.1
031 */
032public interface Mutable<T> {
033
034    /**
035     * Gets the value of this mutable.
036     * 
037     * @return the stored value
038     */
039    T getValue();
040
041    /**
042     * Sets the value of this mutable.
043     * 
044     * @param value
045     *            the value to store
046     * @throws NullPointerException
047     *             if the object is null and null is invalid
048     * @throws ClassCastException
049     *             if the type is invalid
050     */
051    void setValue(T value);
052
053}