*     very rare. Note that if backward conversion is not only unimplemented but
   *     unimplement<i>able</i> (for example, consider a {@code Converter<Chicken, ChickenNugget>}),
   *     then this is not logically a {@code Converter} at all, and should just implement {@link
   *     Function}.
   */
  @ForOverride
  protected abstract A doBackward(B b);

  // API (consumer-side) methods

   * AnnotatedElement}, which {@code TypeVariable} began to extend only in Java 8. Those methods
   * refer only to types present in Java 7, so we could implement them in {@code TypeVariableImpl}
   * today. (We could probably then make {@code TypeVariableImpl} implement {@code AnnotatedElement}
   * so that we get partial compile-time checking.)
   *

    // load timeout multiplier.  Or we could try to use a CPU time bound instead of wall clock time
    // bound.  But these ideas are harder to implement.  We do not try to detect or handle a
    // user-specified -XX:+DisableExplicitGC.
    //
    // TODO(user): Consider using
    // java/lang/management/OperatingSystemMXBean.html#getSystemLoadAverage()
    //

   *   } catch (UncheckedTimeoutException e) {
   *     return DEFAULT_VALUE;
   *   }
   * </pre>
   *
   * @param target the object to proxy
   * @param interfaceType the interface you wish the returned proxy to implement
   * @param timeoutDuration with timeoutUnit, the maximum length of time that callers are willing to
   *     wait on each method call to the proxy

import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/** Static methods used to implement {@link Futures#getChecked(Future, Class)}. */
@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault
final class FuturesGetChecked {
  @CanIgnoreReturnValue
  @ParametricNullness

 * <i>chaining</i>, and <i>using</i>.
 *
 * <h4>Acquiring</h4>
 *
 * <p>The common ways to get an instance of {@code Ordering} are:
 *
 * <ul>
 *   <li>Subclass it and implement {@link #compare} instead of implementing {@link Comparator}
 *       directly
 *   <li>Pass a <i>pre-existing</i> {@link Comparator} instance to {@link #from(Comparator)}
 *   <li>Use the natural ordering, {@link Ordering#natural}

 * states it cannot ever leave them.
 *
 * <p>Implementors of this interface are strongly encouraged to extend one of the abstract classes
 * in this package which implement this interface and make the threading and state management
 * easier.
 *
 * @author Jesse Wilson
 * @author Luke Sandberg
 * @since 9.0 (in 1.0 as {@code com.google.common.base.Service})
 */

 *
 * <p>Popular escapers are defined as constants in classes like {@link
 * com.google.common.html.HtmlEscapers} and {@link com.google.common.xml.XmlEscapers}. To create
 * your own escapers extend this class and implement the {@link #escape(int)} method.
 *
 * @author David Beaumont
 * @since 15.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public abstract class UnicodeEscaper extends Escaper {

   *   implemented below). This is a bit surprising with putIfAbsent, which really becomes
   *   putIfZero.
   *
   * - Allow putIfAbsent and replace to distinguish between zero and absent, but don't implement
   *   remove(K, long). Without any two-phase operations it becomes feasible for all remaining
   *   operations to distinguish between zero and absent. If we do this, then perhaps we should add
   *   replace(key, long).

 *
 * <p>Popular escapers are defined as constants in classes like {@link
 * com.google.common.html.HtmlEscapers} and {@link com.google.common.xml.XmlEscapers}. To create
 * your own escapers extend this class and implement the {@link #escape(int)} method.
 *
 * @author David Beaumont
 * @since 15.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public abstract class UnicodeEscaper extends Escaper {