*   <li>It is easy for the user to ensure that listeners are never invoked while holding locks.
 * </ul>
 *
 * The last point is subtle. Often the observable object will be managing its own internal state
 * using a lock, however it is dangerous to dispatch listeners while holding a lock because they
 * might run on the {@code directExecutor()} or be otherwise re-entrant (call back into your

        "value (%s) is outside the range for an unsigned integer value",
        value);
    return fromIntBits(value.intValue());
  }

  /**
   * Returns an {@code UnsignedInteger} holding the value of the specified {@code String}, parsed as
   * an unsigned {@code int} value.
   *
   * @throws NumberFormatException if the string does not contain a parsable unsigned {@code int}
   *     value
   */

### Holding multiple locks

You're allowed to take the Http2Connection lock while holding the Http2Writer lock. But not vice-versa. Because taking the Http2Writer lock can block.

        "value (%s) is outside the range for an unsigned long value",
        value);
    return fromLongBits(value.longValue());
  }

  /**
   * Returns an {@code UnsignedLong} holding the value of the specified {@code String}, parsed as an
   * unsigned {@code long} value.
   *
   * @throws NumberFormatException if the string does not contain a parsable unsigned {@code long}
   *     value
   */

   * returned future will emulate {@link ListenableFuture#addListener} by taking a thread from an
   * internal, unbounded pool at the first call to {@code addListener} and holding it until the
   * future is {@linkplain Future#isDone() done}.
   *
   * <p>Prefer to create {@code ListenableFuture} instances with {@link SettableFuture}, {@link

import java.util.Comparator;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;
import org.jspecify.annotations.Nullable;

/**
 * An implementation of {@link ImmutableTable} holding an arbitrary number of cells.
 *
 * @author Gregory Kick
 */
@GwtCompatible
abstract class RegularImmutableTable<R, C, V> extends ImmutableTable<R, C, V> {
  RegularImmutableTable() {}

  protected void shutDown() throws Exception {}

  /**
   * Invoked to request the service to stop.
   *
   * <p>By default this method does nothing.
   *
   * <p>Currently, this method is invoked while holding a lock. If an implementation of this method
   * blocks, it can prevent this service from changing state. If you need to performing a blocking
   * operation in order to trigger shutdown, consider instead registering a listener and

   * the String used to construct them is no longer strongly referenced outside of the CipherSuite.
   */
  @Test
  fun instancesAreInterned_survivesGarbageCollection() {
    // We're not holding onto a reference to this String instance outside of the CipherSuite...
    val cs = forJavaName("FakeCipherSuite_instancesAreInterned")
    System.gc() // Unless cs references the String instance, it may now be garbage collected.

  protected void shutDown() throws Exception {}

  /**
   * Invoked to request the service to stop.
   *
   * <p>By default this method does nothing.
   *
   * <p>Currently, this method is invoked while holding a lock. If an implementation of this method
   * blocks, it can prevent this service from changing state. If you need to performing a blocking
   * operation in order to trigger shutdown, consider instead registering a listener and