Java example source code file (CacheReferencesTest.java)

This example Java source code file (CacheReferencesTest.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

cachebuilderfactory, cacheloader, cachereferencestest, countingremovallistener, interruptedexception, iterable, key, key_to_string_loader, loadingcache, object, outofmemoryerror, override, string, weakreference

The CacheReferencesTest.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 static com.google.common.cache.LocalCache.Strength.STRONG;
import static com.google.common.collect.Maps.immutableEntry;
import static com.google.common.truth.Truth.assertThat;

import com.google.common.base.Function;
import com.google.common.cache.LocalCache.Strength;
import com.google.common.cache.TestingRemovalListeners.CountingRemovalListener;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterables;

import junit.framework.TestCase;

import java.lang.ref.WeakReference;

/**
 * Tests of basic {@link LoadingCache} operations with all possible combinations of key & value
 * strengths.
 *
 * @author mike nonemacher
 */
public class CacheReferencesTest extends TestCase {

  private static final CacheLoader<Key,String> KEY_TO_STRING_LOADER =
      new CacheLoader<Key, String>() {
        @Override public String load(Key key) {
          return key.toString();
        }
      };

  private CacheBuilderFactory factoryWithAllKeyStrengths() {
    return new CacheBuilderFactory()
        .withKeyStrengths(ImmutableSet.of(STRONG, Strength.WEAK))
        .withValueStrengths(ImmutableSet.of(STRONG, Strength.WEAK, Strength.SOFT));
  }

  private Iterable<LoadingCache caches() {
    CacheBuilderFactory factory = factoryWithAllKeyStrengths();
    return Iterables.transform(factory.buildAllPermutations(),
        new Function<CacheBuilder>() {
          @Override public LoadingCache<Key, String> apply(CacheBuilder builder) {
            return builder.build(KEY_TO_STRING_LOADER);
          }
        });
  }

  public void testContainsKeyAndValue() {
    for (LoadingCache<Key, String> cache : caches()) {
      // maintain strong refs so these won't be collected, regardless of cache's key/value strength
      Key key = new Key(1);
      String value = key.toString();
      assertSame(value, cache.getUnchecked(key));
      assertTrue(cache.asMap().containsKey(key));
      assertTrue(cache.asMap().containsValue(value));
      assertEquals(1, cache.size());
    }
  }

  public void testClear() {
    for (LoadingCache<Key, String> cache : caches()) {
      Key key = new Key(1);
      String value = key.toString();
      assertSame(value, cache.getUnchecked(key));
      assertFalse(cache.asMap().isEmpty());
      cache.invalidateAll();
      assertEquals(0, cache.size());
      assertTrue(cache.asMap().isEmpty());
      assertFalse(cache.asMap().containsKey(key));
      assertFalse(cache.asMap().containsValue(value));
    }
  }

  public void testKeySetEntrySetValues() {
    for (LoadingCache<Key, String> cache : caches()) {
      Key key1 = new Key(1);
      String value1 = key1.toString();
      Key key2 = new Key(2);
      String value2 = key2.toString();
      assertSame(value1, cache.getUnchecked(key1));
      assertSame(value2, cache.getUnchecked(key2));
      assertEquals(ImmutableSet.of(key1, key2), cache.asMap().keySet());
      assertThat(cache.asMap().values()).containsExactly(value1, value2);
      assertEquals(ImmutableSet.of(immutableEntry(key1, value1), immutableEntry(key2, value2)),
          cache.asMap().entrySet());
    }
  }

  public void testInvalidate() {
    for (LoadingCache<Key, String> cache : caches()) {
      Key key1 = new Key(1);
      String value1 = key1.toString();
      Key key2 = new Key(2);
      String value2 = key2.toString();
      assertSame(value1, cache.getUnchecked(key1));
      assertSame(value2, cache.getUnchecked(key2));
      cache.invalidate(key1);
      assertFalse(cache.asMap().containsKey(key1));
      assertTrue(cache.asMap().containsKey(key2));
      assertEquals(1, cache.size());
      assertEquals(ImmutableSet.of(key2), cache.asMap().keySet());
      assertThat(cache.asMap().values()).contains(value2);
      assertEquals(ImmutableSet.of(immutableEntry(key2, value2)), cache.asMap().entrySet());
    }
  }

  // fails in Maven with 64-bit JDK: http://code.google.com/p/guava-libraries/issues/detail?id=1568

  private void assertCleanup(LoadingCache<Integer, String> cache,
      CountingRemovalListener<Integer, String> removalListener) {

    // initialSize will most likely be 2, but it's possible for the GC to have already run, so we'll
    // observe a size of 1
    long initialSize = cache.size();
    assertTrue(initialSize == 1 || initialSize == 2);

    // wait up to 5s
    byte[] filler = new byte[1024];
    for (int i = 0; i < 500; i++) {
      System.gc();

      CacheTesting.drainReferenceQueues(cache);
      if (cache.size() == 1) {
        break;
      }
      try {
        Thread.sleep(10);
      } catch (InterruptedException e) { /* ignore */}
      try {
        // Fill up heap so soft references get cleared.
        filler = new byte[Math.max(filler.length, filler.length * 2)];
      } catch (OutOfMemoryError e) {}
    }

    CacheTesting.processPendingNotifications(cache);
    assertEquals(1, cache.size());
    assertEquals(1, removalListener.getCount());
  }

  // A simple type whose .toString() will return the same value each time, but without maintaining
  // a strong reference to that value.
  static class Key {
    private final int value;
    private WeakReference<String> toString;

    Key(int value) {
      this.value = value;
    }

    @Override public synchronized String toString() {
      String s;
      if (toString != null) {
        s = toString.get();
        if (s != null) {
          return s;
        }
      }
      s = Integer.toString(value);
      toString = new WeakReference<String>(s);
      return s;
    }
  }
}