* @param <V> the type of the cache's values, which are not permitted to be null
 * @author Charles Fry
 * @since 11.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public interface LoadingCache<K, V> extends Cache<K, V>, Function<K, V> {

  /**
   * Returns the value associated with {@code key} in this cache, first loading that value if

 * @param <V> the type of the cache's values, which are not permitted to be null
 * @author Charles Fry
 * @since 11.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public interface LoadingCache<K, V> extends Cache<K, V>, Function<K, V> {

  /**
   * Returns the value associated with {@code key} in this cache, first loading that value if

  private Iterable<LoadingCache<Object, Object>> caches() {
    // lots of different ways to configure a LoadingCache
    CacheBuilderFactory factory = cacheFactory();
    return Iterables.transform(
        factory.buildAllPermutations(),
        new Function<CacheBuilder<Object, Object>, LoadingCache<Object, Object>>() {
          @Override

   * constructed {@link LoadingCache} as the delegate.
   *
   * @since 10.0
   */
  public abstract static class SimpleForwardingLoadingCache<K, V>
      extends ForwardingLoadingCache<K, V> {
    private final LoadingCache<K, V> delegate;

    protected SimpleForwardingLoadingCache(LoadingCache<K, V> delegate) {
      this.delegate = Preconditions.checkNotNull(delegate);
    }

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

  private void checkExpiration(
      LoadingCache<String, Integer> cache,

  }

  /**
   * Make sure LoadingCache correctly wraps ExecutionExceptions and UncheckedExecutionExceptions.
   */
  public void testLoadingExceptionWithCause() {
    final Exception cause = new Exception();
    final UncheckedExecutionException uee = new UncheckedExecutionException(cause);
    final ExecutionException ee = new ExecutionException(cause);

    LoadingCache<Object, Object> cacheUnchecked =

import junit.framework.TestCase;

/**
 * Unit test for {@link ForwardingLoadingCache}.
 *
 * @author Charles Fry
 */
public class ForwardingLoadingCacheTest extends TestCase {
  private LoadingCache<String, Boolean> forward;
  private LoadingCache<String, Boolean> mock;

  @SuppressWarnings({"unchecked", "DoNotMock"}) // mock
  @Override
  public void setUp() throws Exception {
    super.setUp();
    /*

public class AbstractLoadingCacheTest extends TestCase {

  public void testGetUnchecked_checked() {
    final Exception cause = new Exception();
    final AtomicReference<Object> valueRef = new AtomicReference<>();
    LoadingCache<Object, Object> cache =
        new AbstractLoadingCache<Object, Object>() {
          @Override
          public Object get(Object key) throws ExecutionException {
            Object v = valueRef.get();

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

  private void checkExpiration(
      LoadingCache<String, Integer> cache,

   *
   * <p>This method should be overridden when bulk retrieval is significantly more efficient than
   * many individual lookups. Note that {@link LoadingCache#getAll} will defer to individual calls
   * to {@link LoadingCache#get} if this method is not overridden.
   *
   * @param keys the unique, non-null keys whose values should be loaded