com.google.common.cache.RemovalListener Maven / Gradle / Ivy
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/*
* 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.GwtCompatible;
/**
* An object that can receive a notification when an entry is removed from a cache. The removal
* resulting in notification could have occurred to an entry being manually removed or replaced, or
* due to eviction resulting from timed expiration, exceeding a maximum size, or garbage collection.
*
* 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 the most general type of keys this listener can listen for; for example {@code Object}
* if any key is acceptable
* @param 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
*/
@GwtCompatible
@FunctionalInterface
@ElementTypesAreNonnullByDefault
public interface RemovalListener {
/**
* Notifies the listener that a removal occurred at some point in the past.
*
* This does not always signify that the key is now absent from the cache, as it may have
* already been re-added.
*/
// Technically should accept RemovalNotification, but because
// RemovalNotification is guaranteed covariant, let's make users' lives simpler.
void onRemoval(RemovalNotification notification);
}