* 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

  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);

  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

   * cached value for {@code key}.
   *
   * @since 11.0
   */
  @CanIgnoreReturnValue // TODO(b/27479612): consider removing this?
  @Nullable V getIfPresent(@CompatibleWith("K") Object key);

  /**
   * Returns the value associated with {@code key} in this cache, obtaining that value from {@code

          return newValue;
        } catch (Exception e) {
          throw new ExecutionException(e);
        }
      }
    }

    @Override
    public @Nullable V getIfPresent(Object key) {
      return localCache.getIfPresent(key);
    }

    @Override
    public void put(K key, V value) {
      localCache.put(key, value);
    }

    @Override
    public void invalidate(Object key) {

  public void testGetIfPresent() {
    assertThat(Enums.getIfPresent(TestEnum.class, "CHEETO")).hasValue(TestEnum.CHEETO);
    assertThat(Enums.getIfPresent(TestEnum.class, "HONDA")).hasValue(TestEnum.HONDA);
    assertThat(Enums.getIfPresent(TestEnum.class, "POODLE")).hasValue(TestEnum.POODLE);

    assertThat(Enums.getIfPresent(TestEnum.class, "CHEETO")).isPresent();
    assertThat(Enums.getIfPresent(TestEnum.class, "HONDA")).isPresent();

    fakeTicker.advance(999, MILLISECONDS);
    assertThat(cache.getIfPresent(10)).isEqualTo(100);
    assertThat(cache.getIfPresent(20)).isEqualTo(200);
    assertThat(cache.getIfPresent(4)).isEqualTo(2);

    fakeTicker.advance(2, MILLISECONDS);
    assertThat(cache.getIfPresent(10)).isNull();
    assertThat(cache.getIfPresent(20)).isNull();
    assertThat(cache.getIfPresent(4)).isNull();

    cache.put(10, 20);

    fakeTicker.advance(999, MILLISECONDS);
    assertThat(cache.getIfPresent(10)).isEqualTo(100);
    assertThat(cache.getIfPresent(20)).isEqualTo(200);
    assertThat(cache.getIfPresent(4)).isEqualTo(2);

    fakeTicker.advance(2, MILLISECONDS);
    assertThat(cache.getIfPresent(10)).isNull();
    assertThat(cache.getIfPresent(20)).isNull();
    assertThat(cache.getIfPresent(4)).isNull();

    cache.put(10, 20);