/*
* 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 com.google.common.annotations.Beta;
/**
* An object that can receive a notification when an entry is removed from a cache. The removal
* resulting in notification could have occured to an entry being manually removed or replaced, or
* due to eviction resulting from timed expiration, exceeding a maximum size, or garbage
* collection.
*
* <p>An instance may be called concurrently by multiple threads to process different entries.
* Implementations of this interface should avoid performing blocking calls or synchronizing on
* shared resources.
*
* @param <K> the most general type of keys this listener can listen for; for
* example {@code Object} if any key is acceptable
* @param <V> the most general type of values this listener can listen for; for
* example {@code Object} if any key is acceptable
* @author Charles Fry
* @since 10.0
*/
@Beta
public interface RemovalListener<K, V> {
/**
* Notifies the listener that a removal occurred at some point in the past.
*/
// Technically should accept RemovalNotification<? extends K, ? extends V>, but because
// RemovalNotification is guaranteed covariant, let's make users' lives simpler.
void onRemoval(RemovalNotification<K, V> notification);
}
|