public static CharMatcher invisible() {
    return Invisible.INSTANCE;
  }

  /**
   * Determines whether a character is single-width (not double-width). When in doubt, this matcher
   * errs on the side of returning {@code false} (that is, it tends to assume a character is
   * double-width).
   *
   * <p><b>Note:</b> as the reference file evolves, we will modify this matcher to keep it up to
   * date.
   *

  public static CharMatcher invisible() {
    return Invisible.INSTANCE;
  }

  /**
   * Determines whether a character is single-width (not double-width). When in doubt, this matcher
   * errs on the side of returning {@code false} (that is, it tends to assume a character is
   * double-width).
   *
   * <p><b>Note:</b> as the reference file evolves, we will modify this matcher to keep it up to
   * date.
   *

   * requests become more likely to trigger expensive operations (a more extreme case of this
   * example is when a server has just booted, and it is mostly busy with getting itself up to
   * speed).
   *
   * To deal with such scenarios, we add an extra dimension, that of "past underutilization",
   * modeled by "storedPermits" variable. This variable is zero when there is no underutilization,

   * href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Viewport-Width">{@code
   * Viewport-Width}</a> header field name.
   *
   * @since 31.0
   */
  public static final String VIEWPORT_WIDTH = "Viewport-Width";

  /**
   * The HTTP <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Width">{@code
   * Width}</a> header field name.
   *
   * @since 31.0
   */

  @ListFeature.Require(SUPPORTS_ADD_WITH_INDEX)
  @CollectionSize.Require(absent = ZERO)
  public void testAddAllAtIndex_supportedAllPresent() {
    assertTrue(
        "addAll(n, allPresent) should return true",
        getList().addAll(0, MinimalCollection.of(e0())));
    expectAdded(0, e0());
  }

  @ListFeature.Require(absent = SUPPORTS_ADD_WITH_INDEX)
  @CollectionSize.Require(absent = ZERO)

 */
@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
   * necessary. No observable state associated with this cache is modified until loading completes.
   *
   * <p>If another call to {@link #get} or {@link #getUnchecked} is currently loading the value for

   *
   * <p>The difference with {@link #callWithTimeout(Callable, long, TimeUnit)} is that this method
   * will ignore interrupts on the current thread.
   *
   * @param callable the Callable to execute
   * @param timeoutDuration with timeoutUnit, the maximum length of time to wait
   * @param timeoutUnit with timeoutDuration, the maximum length of time to wait

 *       other tests. We want to exclude the other tests (which Android can't handle) while
 *       continuing to run {@code FooTest} itself. This is exactly what happens with {@code
 *       AndroidIncompatible}. But I'm not sure what would happen if we annotated the {@code
 *       suite()} method with {@code Suppress}. Would {@code FooTest} itself be suppressed, too?
 *   <li>In at least one case, a use of {@code sun.misc.FpUtils}, the test will not even

 *
 * <ul>
 *   <li>DISABLED
 *   <li>WARN
 *   <li>THROW
 * </ul>
 *
 * <p>The locks created by a factory instance will detect lock acquisition cycles with locks created
 * by other {@code CycleDetectingLockFactory} instances (except those with {@code Policy.DISABLED}).
 * A lock's behavior when a cycle is detected, however, is defined by the {@code Policy} of the

  /**
   * Returns the value associated with {@code key} in this cache, or {@code null} if there is no
   * cached value for {@code key}.
   *
   * @since 11.0
   */
  @CheckForNull
  @CanIgnoreReturnValue // TODO(b/27479612): consider removing this?
  V getIfPresent(@CompatibleWith("K") Object key);

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