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 * {@link Mutable} is used as a generic interface to the implementations in this package.
024 * </p>
025 * <p>
026 * A typical use case would be to enable a primitive or string to be passed to a method and allow that method to
027 * effectively change the value of the primitive/string. Another use case is to store a frequently changing primitive in
028 * a collection (for example a total in a map) without needing to create new Integer/Long wrapper objects.
029 * </p>
030 *
031 * @param <T> the type to set and get
032 * @since 2.1
033 */
034public interface Mutable<T> {
035
036    /**
037     * Gets the value of this mutable.
038     *
039     * @return the stored value
040     */
041    T getValue();
042
043    /**
044     * Sets the value of this mutable.
045     *
046     * @param value
047     *            the value to store
048     * @throws NullPointerException
049     *             if the object is null and null is invalid
050     * @throws ClassCastException
051     *             if the type is invalid
052     */
053    void setValue(T value);
054
055}