Set<E> delegate = delegateOrNull();
    if (delegate != null) {
      metadata =
          Ints.constrainToRange(size(), CompactHashing.DEFAULT_SIZE, CompactHashing.MAX_SIZE);
      delegate.clear(); // invalidate any iterators left over!
      table = null;
      size = 0;
    } else {
      Arrays.fill(requireElements(), 0, size, null);
      CompactHashing.tableClear(requireTable());

    assertThat(wrappedSet).isEqualTo(copyOfWrappedSet);

    // test that setToTest is still valid
    assertThat(setToTest).isEqualTo(wrappedSet);
    assertThat(setToTest).isEqualTo(copyOfWrappedSet);

    // invalidate setToTest
    wrappedSet.remove(1);
    // sanity check on update of wrappedSet
    assertThat(wrappedSet).isNotEqualTo(copyOfWrappedSet);

// do not require all metadata to be synchronized with the disk.
func Fdatasync(f *os.File) error {
	return syscall.Fdatasync(int(f.Fd()))
}

// FadviseDontNeed invalidates page-cache
func FadviseDontNeed(f *os.File) error {
	return unix.Fadvise(int(f.Fd()), 0, 0, unix.FADV_DONTNEED)

    assertThat(wrappedSet).isEqualTo(copyOfWrappedSet);

    // test that setToTest is still valid
    assertThat(setToTest).isEqualTo(wrappedSet);
    assertThat(setToTest).isEqualTo(copyOfWrappedSet);

    // invalidate setToTest
    wrappedSet.remove(1);
    // sanity check on update of wrappedSet
    assertThat(wrappedSet).isNotEqualTo(copyOfWrappedSet);

    cache.put(0, 10);

    assertEquals(Integer.valueOf(10), cache.get(0, loader));
    assertEquals(Integer.valueOf(1), cache.get(20, loader));
    assertEquals(Integer.valueOf(2), cache.get(34, loader));

    cache.invalidate(0);
    assertEquals(Integer.valueOf(3), cache.get(0, loader));

    cache.put(0, 10);
    cache.invalidateAll();
    assertEquals(Integer.valueOf(4), cache.get(0, loader));
  }

            try {
                final StatsObject data = statsCache.getIfPresent(key);
                if (data != null && data.decrement() <= 0) {
                    statsCache.invalidate(key);
                    final Long begin = data.remove(BEGIN_KEY);
                    if (begin != null) {
                        printStats(keyObj, data, begin, true);
                    }
                }

 * @since 10.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public enum RemovalCause {
  /**
   * The entry was manually removed by the user. This can result from the user invoking {@link
   * Cache#invalidate}, {@link Cache#invalidateAll(Iterable)}, {@link Cache#invalidateAll()}, {@link
   * Map#remove}, {@link ConcurrentMap#remove}, or {@link Iterator#remove}.
   */
  EXPLICIT {
    @Override
    boolean wasEvicted() {

  override fun getValue(s: String): Any {
    throw UnsupportedOperationException()
  }

  override fun getValueNames(): Array<String> {
    throw UnsupportedOperationException()
  }

  override fun invalidate() {
    throw UnsupportedOperationException()
  }

  override fun isValid(): Boolean {
    throw UnsupportedOperationException()
  }

 * {@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
 * in terms of {@link #invalidate}. The method {@link #cleanUp} is a no-op. All other methods throw
 * an {@link UnsupportedOperationException}.
 *
 * @author Charles Fry
 * @since 11.0
 */
@GwtIncompatible
@ElementTypesAreNonnullByDefault

   *
   * <p>If {@code node} is removed from the graph after this method is called, the {@code Set}
   * {@code view} returned by this method will be invalidated, and will throw {@code
   * IllegalStateException} if it is accessed in any way, with the following exceptions:
   *
   * <ul>
   *   <li>{@code view.equals(view)} evaluates to {@code true} (but any other {@code equals()}