*   // do other things since the monitor was not available
 * }
 * }</pre>
 *
 * <h2>Comparison with {@code synchronized} and {@code ReentrantLock}</h2>
 *
 * <p>The following examples show a simple threadsafe holder expressed using {@code synchronized},
 * {@link ReentrantLock}, and {@code Monitor}.
 *
 * <h3>{@code synchronized}</h3>
 *
 * <p>This version is the fewest lines of code, largely because the synchronization mechanism used

import org.codelibs.core.net.URLUtil;
import org.codelibs.core.nio.ChannelUtil;

/**
 * コピーのためのユーティリティです。
 * <p>
 * コピー可能な入力と出力の組み合わせと、コピーされる要素の単位は以下のとおりです。
 * </p>
 * <table border="1">
 * <caption>Elements for coping instances</caption>
 * <tr>
 * <th rowspan="2">入力の型</th>
 * <th colspan="4">出力の型</th>
 * </tr>
 * <tr>
 * <th>{@link OutputStream}</th>
 * <th>{@link Writer}</th>

    WatchedCreatorLoader loader = new WatchedCreatorLoader();
    LoadingCache<String, Integer> cache =
        CacheBuilder.newBuilder()
            .expireAfterWrite(EXPIRING_TIME, MILLISECONDS)
            .removalListener(removalListener)
            .ticker(ticker)
            .build(loader);
    checkExpiration(cache, loader, ticker, removalListener);
  }

    final Map<Path, Holder> modelByPath = new ConcurrentHashMap<>();

    final Map<GAKey, Holder> modelByGA = new ConcurrentHashMap<>();

    public static class Holder {
        private volatile boolean set;
        private volatile Model model;

        Holder() {}

        Holder(Model model) {
            this.model = Objects.requireNonNull(model);

  public void testBulkLoad_loadAll() throws ExecutionException {
    IdentityLoader<Integer> backingLoader = identityLoader();
    CacheLoader<Integer, Integer> loader = bulkLoader(backingLoader);
    LoadingCache<Integer, Integer> cache = CacheBuilder.newBuilder().recordStats().build(loader);
    CacheStats stats = cache.stats();
    assertEquals(0, stats.missCount());
    assertEquals(0, stats.loadSuccessCount());

   * {@linkplain Thread#getContextClassLoader() context class loader}. In simple environments, the
   * context class loader will find resources from the class path. In environments where different
   * threads can have different class loaders, for example app servers, the context class loader
   * will typically have been set to an appropriate loader for the current thread.
   *

    CountingLoader loader = new CountingLoader();
    LocalCache<Object, Object> map = makeLocalCache(createCacheBuilder());
    assertEquals(0, loader.getCount());

    Object key = new Object();
    Object value = map.get(key, loader);
    assertEquals(1, loader.getCount());
    assertEquals(value, map.get(key, loader));
    assertEquals(1, loader.getCount());
  }

    CountingLoader loader = new CountingLoader();
    LocalCache<Object, Object> map = makeLocalCache(createCacheBuilder());
    assertEquals(0, loader.getCount());

    Object key = new Object();
    Object value = map.get(key, loader);
    assertEquals(1, loader.getCount());
    assertEquals(value, map.get(key, loader));
    assertEquals(1, loader.getCount());
  }

   *       CacheLoader#loadAll bulk loading implementations}
   * </ul>
   *
   * <p><b>Warning:</b> For any given key, every {@code loader} used with it should compute the same
   * value. Otherwise, a call that passes one {@code loader} may return the result of another call
   * with a differently behaving {@code loader}. For example, a call that requests a short timeout
   * for an RPC may wait for a similar call that requests a long timeout, or a call by an

                Model model = findRawModel(from, gId, aId);
                if (model != null) {
                    context.modelByGA.put(new GAKey(gId, aId), new Holder(model));
                    context.modelByPath.put(model.getPomFile(), new Holder(model));
                }
                return model;
            }

            @Override
            public Model getRawModel(Path from, Path path) {