guava/src/com/google/common/cache/RemovalListeners.java

/*
 * Copyright (C) 2011 The Guava Authors
 *
 * 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.google.common.cache;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.Beta;

import java.util.concurrent.Executor;

/**
 * A collection of common removal listeners.
 *
 * @author Charles Fry
 * @since 10.0
 */
@Beta
public final class RemovalListeners {

  private RemovalListeners() {}

  /**
   * Returns a {@code RemovalListener} which processes all eviction
   * notifications using {@code executor}.
   *
   * @param listener the backing listener
   * @param executor the executor with which removal notifications are
   *     asynchronously executed
   */
  public static <K, V> RemovalListener<K, V> asynchronous(
      final RemovalListener<K, V> listener, final Executor executor) {
    checkNotNull(listener);
    checkNotNull(executor);
    return new RemovalListener<K, V>() {
      @Override
      public void onRemoval(final RemovalNotification<K, V> notification) {
        executor.execute(new Runnable() {
          @Override
          public void run() {
            listener.onRemoval(notification);
          }
        });
      }
    };
  }

}