content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  
  package org.apache.bookkeeper.common.util;
  
  /**
   * A class can implement the <code>Watcher</code> interface when it
   * wants to be informed of <i>one-time</i> changes in watchable objects.
   */
  public interface Watcher<T> {
  
      /**
       * This method is called whenever the watched object is changed. An
       * application calls an <tt>Watchable</tt> object's
       * <code>notifyWatchers</code> method to have all the object's
       * watchers notified of the change.
       *
       * @param value the updated value of a watchable
       */
      void update(T value);
  
  }
  