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    
018    package 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     * @since 2.1
030     * @param <T> the type to set and get 
031     * @version $Id: Mutable.java 1153213 2011-08-02 17:35:39Z ggregory $
032     */
033    public interface Mutable<T> {
034    
035        /**
036         * Gets the value of this mutable.
037         * 
038         * @return the stored value
039         */
040        T getValue();
041    
042        /**
043         * Sets the value of this mutable.
044         * 
045         * @param value
046         *            the value to store
047         * @throws NullPointerException
048         *             if the object is null and null is invalid
049         * @throws ClassCastException
050         *             if the type is invalid
051         */
052        void setValue(T value);
053    
054    }