| /* |
| * 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. |
| * |
| * <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 |
| @FunctionalInterface |
| 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); |
| } |