    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    package org.apache.commons.lang3.concurrent;
    018
    019    /**
    020     * <p>
    021     * Definition of an interface for the thread-safe initialization of objects.
    022     * </p>
    023     * <p>
    024     * The idea behind this interface is to provide access to an object in a
    025     * thread-safe manner. A {@code ConcurrentInitializer} can be passed to multiple
    026     * threads which can all access the object produced by the initializer. Through
    027     * the {@link #get()} method the object can be queried.
    028     * </p>
    029     * <p>
    030     * Concrete implementations of this interface will use different strategies for
    031     * the creation of the managed object, e.g. lazy initialization or
    032     * initialization in a background thread. This is completely transparent to
    033     * client code, so it is possible to change the initialization strategy without
    034     * affecting clients.
    035     * </p>
    036     *
    037     * @author Apache Software Foundation
    038     * @version $Id: ConcurrentInitializer.java 930816 2010-04-05 07:57:10Z bayard $
    039     * @param <T> the type of the object managed by this initializer class
    040     */
    041    public interface ConcurrentInitializer<T> {
    042        /**
    043         * Returns the fully initialized object produced by this {@code
    044         * ConcurrentInitializer}. A concrete implementation here returns the
    045         * results of the initialization process. This method may block until
    046         * results are available. Typically, once created the result object is
    047         * always the same.
    048         *
    049         * @return the object created by this {@code ConcurrentException}
    050         * @throws ConcurrentException if an error occurred during initialization of
    051         * the object
    052         */
    053        T get() throws ConcurrentException;
    054    }