* example involving two locks and two threads, deadlock occurs when one thread acquires Lock A, and
 * then Lock B, while another thread acquires Lock B, and then Lock A:
 *
 * <pre>
 * Thread1: acquire(LockA) --X acquire(LockB)
 * Thread2: acquire(LockB) --X acquire(LockA)
 * </pre>
 *
 * <p>Neither thread will progress because each is waiting for the other. In more complex

   * and returns that value on subsequent calls to {@code get()}. See: <a
   * href="http://en.wikipedia.org/wiki/Memoization">memoization</a>
   *
   * <p>The returned supplier is thread-safe. The delegate's {@code get()} method will be invoked at
   * most once unless the underlying {@code get()} throws an exception. The supplier's serialized

   * and returns that value on subsequent calls to {@code get()}. See: <a
   * href="http://en.wikipedia.org/wiki/Memoization">memoization</a>
   *
   * <p>The returned supplier is thread-safe. The delegate's {@code get()} method will be invoked at
   * most once unless the underlying {@code get()} throws an exception. The supplier's serialized

     * Waits for a value that may still be loading. Unlike get(), this method can block (in the case
     * of FutureValueReference).
     *
     * @throws ExecutionException if the loading thread throws an exception
     * @throws ExecutionError if the loading thread throws an error
     */
    V waitForValue() throws ExecutionException;

    /** Returns the weight of this entry. This is assumed to be static between calls to setValue. */

     * Waits for a value that may still be loading. Unlike get(), this method can block (in the case
     * of FutureValueReference).
     *
     * @throws ExecutionException if the loading thread throws an exception
     * @throws ExecutionError if the loading thread throws an error
     */
    V waitForValue() throws ExecutionException;

    /** Returns the weight of this entry. This is assumed to be static between calls to setValue. */

     * cleaning up from the read thread.
     */
    void postReadCleanup() {
      if ((readCount.incrementAndGet() & DRAIN_THRESHOLD) == 0) {
        runCleanup();
      }
    }

    /**
     * Performs routine cleanup prior to executing a write. This should be called every time a write
     * thread acquires the segment lock, immediately after acquiring the lock.
     */

     * cleaning up from the read thread.
     */
    void postReadCleanup() {
      if ((readCount.incrementAndGet() & DRAIN_THRESHOLD) == 0) {
        runCleanup();
      }
    }

    /**
     * Performs routine cleanup prior to executing a write. This should be called every time a write
     * thread acquires the segment lock, immediately after acquiring the lock.
     */

      return "Maps.asConverter(" + bimap + ")";
    }

    @GwtIncompatible @J2ktIncompatible private static final long serialVersionUID = 0L;
  }

  /**
   * Returns a synchronized (thread-safe) bimap backed by the specified bimap. In order to guarantee
   * serial access, it is critical that <b>all</b> access to the backing bimap is accomplished
   * through the returned bimap.
   *

      return "Maps.asConverter(" + bimap + ")";
    }

    @GwtIncompatible @J2ktIncompatible private static final long serialVersionUID = 0L;
  }

  /**
   * Returns a synchronized (thread-safe) bimap backed by the specified bimap. In order to guarantee
   * serial access, it is critical that <b>all</b> access to the backing bimap is accomplished
   * through the returned bimap.
   *

   * (Specifically, {@code directExecutor} functions should avoid heavyweight operations inside
   * {@code AsyncClosingFunction.apply}. Any heavyweight operations should occur in other threads
   * responsible for completing the returned {@code ClosingFuture}.)
   *
   * <p>After calling this method, you may not call {@link #finishToFuture()}, {@link