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Java example source code file (TestingRemovalListeners.java)

This example Java source code file (TestingRemovalListeners.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

atomicinteger, concurrentlinkedqueue, countingremovallistener, gwtcompatible, gwtincompatible, nullremovallistener, override, queuingremovallistener, removalnotification, testingremovallisteners, threading, threads

The TestingRemovalListeners.java Java example source code

/*
 * 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 nullRemovalListener() {
    return new NullRemovalListener<K, V>();
  }

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

  /**
   * Type-inferring factory method for creating a {@link CountingRemovalListener}.
   */
  static <K, V> CountingRemovalListener 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>
      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 {
    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 {
    @Override
    public void onRemoval(RemovalNotification<K, V> notification) {}
  }
}

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