guava-tests/test/com/google/common/cache/TestingRemovalListeners.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 com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;

import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * Utility {@link RemovalListener} implementations intended for use in testing.
 *
 * @author mike nonemacher
 */
@GwtCompatible(emulated = true)
class TestingRemovalListeners {

  /**
   * Returns a new no-op {@code RemovalListener}.
   */
  static <K, V> NullRemovalListener<K, V> nullRemovalListener() {
    return new NullRemovalListener<K, V>();
  }

  /**
   * Type-inferring factory method for creating a {@link QueuingRemovalListener}.
   */
  @GwtIncompatible("ConcurrentLinkedQueue")
  static <K, V> QueuingRemovalListener<K, V> queuingRemovalListener() {
    return new QueuingRemovalListener<K,V>();
  }

  /**
   * Type-inferring factory method for creating a {@link CountingRemovalListener}.
   */
  static <K, V> CountingRemovalListener<K, V> countingRemovalListener() {
    return new CountingRemovalListener<K,V>();
  }

  /**
   * {@link RemovalListener} that adds all {@link RemovalNotification} objects to a queue.
   */
  @GwtIncompatible("ConcurrentLinkedQueue")
  static class QueuingRemovalListener<K, V>
      extends ConcurrentLinkedQueue<RemovalNotification<K, V>> implements RemovalListener<K, V> {

    @Override
    public void onRemoval(RemovalNotification<K, V> notification) {
      add(notification);
    }
  }

  /**
   * {@link RemovalListener} that counts each {@link RemovalNotification} it receives, and provides
   * access to the most-recently received one.
   */
  static class CountingRemovalListener<K, V> implements RemovalListener<K, V> {
    private final AtomicInteger count = new AtomicInteger();
    private volatile RemovalNotification<K, V> lastNotification;

    @Override
    public void onRemoval(RemovalNotification<K, V> notification) {
      count.incrementAndGet();
      lastNotification = notification;
    }

    public int getCount() {
      return count.get();
    }

    public K getLastEvictedKey() {
      return lastNotification.getKey();
    }

    public V getLastEvictedValue() {
      return lastNotification.getValue();
    }

    public RemovalNotification<K, V> getLastNotification() {
      return lastNotification;
    }
  }

  /**
   * No-op {@link RemovalListener}.
   */
  static class NullRemovalListener<K, V> implements RemovalListener<K, V> {
    @Override
    public void onRemoval(RemovalNotification<K, V> notification) {}
  }
}