content: /*
   * Copyright 1999-2018 Alibaba Group Holding Ltd.
   *
   * Licensed 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 com.alibaba.nacos.common.utils;
  
  /**
   * Obeserver.
   *
   * @author <a href="mailto:liaochuntao@live.com">liaochuntao</a>
   * @author xiweng.yy
   */
  public interface Observer {
      
      /**
       * This method is called whenever the observed object is changed. An application calls an {@code Observable}
       * object's {@code notifyObservers} method to have all the object's observers notified of the change.
       *
       * @param o the observable object.
       */
      void update(Observable o);
      
  }
  