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  /*
   * Copyright 2010 Google Inc. All Rights Reserved.
   *
   * 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
   *
   *     https://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.cayenne.util.concurrentlinkedhashmap;
  
  /**
   * A listener registered for notification when an entry is evicted. An instance may be
   * called concurrently by multiple threads to process entries. An implementation should
   * avoid performing blocking calls or synchronizing on shared resources.
   * <p>
   * The listener is invoked by {@link ConcurrentLinkedHashMap} on a caller's thread and
   * will not block other threads from operating on the map. An implementation should be
   * aware that the caller's thread will not expect long execution times or failures as a
   * side effect of the listener being notified. Execution safety and a fast turn around
   * time can be achieved by performing the operation asynchronously, such as by submitting
   * a task to an {@link java.util.concurrent.ExecutorService}.
   */
  interface EvictionListener<K, V> {
  
      /**
       * A call-back notification that the entry was evicted.
       * 
       * @param key the entry's key
       * @param value the entry's value
       */
      void onEviction(K key, V value);
  }
  