if (v == null) {
              throw new ExecutionException(cause);
            }
            return v;
          }

          @Override
          public @Nullable Object getIfPresent(Object key) {
            return valueRef.get();
          }
        };

    UncheckedExecutionException expected =
        assertThrows(UncheckedExecutionException.class, () -> cache.getUnchecked(new Object()));

        new AbstractCache<Object, Object>() {
          @Override
          public @Nullable Object getIfPresent(Object key) {
            return valueRef.get();
          }
        };

    assertThat(cache.getIfPresent(new Object())).isNull();

    Object newValue = new Object();
    valueRef.set(newValue);
    assertThat(cache.getIfPresent(new Object())).isSameInstanceAs(newValue);
  }

  public void testGetAllPresent_empty() {

 * implementation for the {@link #get(Object)} and {@link #getIfPresent} methods. {@link
 * #getUnchecked}, {@link #get(Object, Callable)}, and {@link #getAll} are implemented in terms of
 * {@code get}; {@link #getAllPresent} is implemented in terms of {@code getIfPresent}; {@link
 * #putAll} is implemented in terms of {@link #put}, {@link #invalidateAll(Iterable)} is implemented

 * implementation for the {@link #get(Object)} and {@link #getIfPresent} methods. {@link
 * #getUnchecked}, {@link #get(Object, Callable)}, and {@link #getAll} are implemented in terms of
 * {@code get}; {@link #getAllPresent} is implemented in terms of {@code getIfPresent}; {@link
 * #putAll} is implemented in terms of {@link #put}, {@link #invalidateAll(Iterable)} is implemented

 *
 * <p>To implement a cache, the programmer needs only to extend this class and provide an
 * implementation for the {@link #put} and {@link #getIfPresent} methods. {@link #getAllPresent} is
 * implemented in terms of {@link #getIfPresent}; {@link #putAll} is implemented in terms of {@link
 * #put}, {@link #invalidateAll(Iterable)} is implemented in terms of {@link #invalidate}. The

  protected ForwardingCache() {}

  @Override
  protected abstract Cache<K, V> delegate();

  /**
   * @since 11.0
   */
  @Override
  public @Nullable V getIfPresent(Object key) {
    return delegate().getIfPresent(key);
  }

  /**
   * @since 11.0
   */
  @Override
  public V get(K key, Callable<? extends V> valueLoader) throws ExecutionException {
    return delegate().get(key, valueLoader);

   * user input or falling back to a default enum constant. For example, {@code
   * Enums.getIfPresent(Country.class, countryInput).or(Country.DEFAULT);}
   *
   * @since 12.0
   */
  public static <T extends Enum<T>> Optional<T> getIfPresent(Class<T> enumClass, String value) {
    checkNotNull(enumClass);
    checkNotNull(value);
    return Platform.getEnumIfPresent(enumClass, value);

  protected ForwardingCache() {}

  @Override
  protected abstract Cache<K, V> delegate();

  /**
   * @since 11.0
   */
  @Override
  public @Nullable V getIfPresent(Object key) {
    return delegate().getIfPresent(key);
  }

  /**
   * @since 11.0
   */
  @Override
  public V get(K key, Callable<? extends V> valueLoader) throws ExecutionException {
    return delegate().get(key, valueLoader);

 *
 * <p>To implement a cache, the programmer needs only to extend this class and provide an
 * implementation for the {@link #put} and {@link #getIfPresent} methods. {@link #getAllPresent} is
 * implemented in terms of {@link #getIfPresent}; {@link #putAll} is implemented in terms of {@link
 * #put}, {@link #invalidateAll(Iterable)} is implemented in terms of {@link #invalidate}. The

   * user input or falling back to a default enum constant. For example, {@code
   * Enums.getIfPresent(Country.class, countryInput).or(Country.DEFAULT);}
   *
   * @since 12.0
   */
  public static <T extends Enum<T>> Optional<T> getIfPresent(Class<T> enumClass, String value) {
    checkNotNull(enumClass);
    checkNotNull(value);
    return Platform.getEnumIfPresent(enumClass, value);