Java tutorial
/* * 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 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 */ @GwtCompatible public interface RemovalListener<K, V> { /** * Notifies the listener that a removal occurred at some point in the past. * * <p>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<? extends K, ? extends V>, but because // RemovalNotification is guaranteed covariant, let's make users' lives simpler. void onRemoval(RemovalNotification<K, V> notification); }