* @param <V> the type of the cache's values, which are not permitted to be null
 * @author Charles Fry
 * @since 11.0
 */
@GwtCompatible
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
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

/**
 * {@link LoadingCache} tests that deal with empty caches.
 *
 * @author mike nonemacher
 */

@NullUnmarked
public class EmptyCachesTest extends TestCase {

  public void testEmpty() {
    for (LoadingCache<Object, Object> cache : caches()) {
      checkEmpty(cache);
    }
  }


  public void testInvalidate_empty() {
    for (LoadingCache<Object, Object> cache : caches()) {

   *
   * <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

  }

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

    LoadingCache<Object, Object> cacheUnchecked =

  public void testSize_populated() {
    for (LoadingCache<Object, Object> cache : caches()) {
      // don't let the entries get GCed
      List<Entry<Object, Object>> unused = warmUp(cache);
      assertThat(cache.size()).isEqualTo(WARMUP_SIZE);
      assertMapSize(cache.asMap(), WARMUP_SIZE);
      checkValidState(cache);
    }
  }

  public void testContainsKey_found() {
    for (LoadingCache<Object, Object> cache : caches()) {

  }

  private Iterable<LoadingCache<Key, String>> caches() {
    CacheBuilderFactory factory = factoryWithAllKeyStrengths();
    return Iterables.transform(
        factory.buildAllPermutations(), builder -> builder.build(KEY_TO_STRING_LOADER));
  }

  public void testContainsKeyAndValue() {
    for (LoadingCache<Key, String> cache : caches()) {

   *
   * <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

    for (int i = 1; i < 1000; i++) {
      LoadingCache<Object, Object> cache = CacheBuilder.newBuilder().maximumSize(i).build(loader);
      assertThat(CacheTesting.getTotalSegmentSize(cache)).isEqualTo(i);
    }
  }

  public void testEviction_setMaxSegmentWeight() {
    IdentityLoader<Object> loader = identityLoader();
    for (int i = 1; i < 1000; i++) {
      LoadingCache<Object, Object> cache =

   * 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);
    }