https://github.com/Terracotta-OSS/statistics: A statistics framework used inside Ehcache and the Terracotta products 
/*
 * All content copyright Terracotta, Inc., unless otherwise indicated.
 *
 * 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.
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package org.terracotta.statistics.observer;


The marker interface implemented by all statistic observer classes.


A statistic observer presents methods used to update a statistic.  There are
two general classes of observer implementations:

    

  1. Initial observers are called by product code in order to record the
occurrence of a product related 'event'
    2. 

  2. Derived observers are called by other observers with then intention of
tracking higher order statistics.
    3. 



/**
 * The marker interface implemented by all statistic observer classes.
 * <p>
 * A statistic observer presents methods used to update a statistic.  There are
 * two general classes of observer implementations:
 * <ol>
 * <li>Initial observers are called by product code in order to record the
 * occurrence of a product related 'event'</li>
 * <li>Derived observers are called by other observers with then intention of
 * tracking higher order statistics.</li>
 * </ol>
 */
public interface ChainedObserver {

}