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    1   /*
    2    * Licensed to the Apache Software Foundation (ASF) under one or more
    3    * contributor license agreements. See the NOTICE file distributed with
    4    * this work for additional information regarding copyright ownership.
    5    * The ASF licenses this file to You under the Apache license, Version 2.0
    6    * (the "License"); you may not use this file except in compliance with
    7    * the License. You may obtain a copy of the License at
    8    *
    9    *      http://www.apache.org/licenses/LICENSE-2.0
    10   *
    11   * Unless required by applicable law or agreed to in writing, software
    12   * distributed under the License is distributed on an "AS IS" BASIS,
    13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    14   * See the license for the specific language governing permissions and
    15   * limitations under the license.
    16   */
    17
    18  package org.apache.logging.log4j.core;
    19
    20  /**
    21   * All proper Java frameworks implement some sort of object life cycle. In Log4j, the main interface for handling
    22   * the life cycle context of an object is this one. An object first starts in the {@link State#INITIALIZED} state
    23   * by default to indicate the class has been loaded. From here, calling the {@link #start()} method will change this
    24   * state to {@link State#STARTING}. After successfully being started, this state is changed to {@link State#STARTED}.
    25   * When the {@link #stop()} is called, this goes into the {@link State#STOPPING} state. After successfully being
    26   * stopped, this goes into the {@link State#STOPPED} state. In most circumstances, implementation classes should
    27   * store their {@link State} in a {@code volatile} field or inside an
    28   * {@link java.util.concurrent.atomic.AtomicReference} dependent on synchronization and concurrency requirements.
    29   */
    30  public interface LifeCycle {
    31
    32      /**
    33       * Status of a life cycle like a {@link LoggerContext}.
    34       */
    35      public enum State {
    36          /** Initialized but not yet started. */
    37          INITIALIZED,
    38          /** In the process of starting. */
    39          STARTING,
    40          /** Has started. */
    41          STARTED,
    42          /** Stopping is in progress. */
    43          STOPPING,
    44          /** Has stopped. */
    45          STOPPED
    46      }
    47
    48      /**
    49       * Gets the life-cycle state
    50       *
    51       * @return the life-cycle state
    52       */
    53      State getState();
    54
    55      void start();
    56
    57      void stop();
    58
    59      boolean isStarted();
    60
    61      boolean isStopped();
    62  }