* {@code NavigableMap}. In many cases, you may wish to override {@link
   * ForwardingNavigableMap#descendingMap} to forward to this implementation or a subclass thereof.
   *
   * <p>In particular, this map iterates over entries with repeated calls to {@link
   * NavigableMap#lowerEntry}. If a more efficient means of iteration is available, you may wish to
   * override the {@code entryIterator()} method of this class.
   *

   * @param to the destination file
   * @throws IOException if an I/O error occurs
   * @throws IllegalArgumentException if {@code from.equals(to)}
   */
  public static void copy(File from, File to) throws IOException {
    checkArgument(!from.equals(to), "Source %s and destination %s must be different", from, to);
    asByteSource(from).copyTo(asByteSink(to));
  }

  /**

   * #clear} to forward to this implementation.
   *
   * @since 7.0
   */
  protected void standardClear() {
    Iterators.clear(iterator());
  }

  /**
   * A sensible definition of {@link #isEmpty} as {@code !iterator().hasNext}. If you override
   * {@link #isEmpty}, you may wish to override {@link #isEmpty} to forward to this implementation.

/**
 * A navigable set which forwards all its method calls to another navigable set. Subclasses should
 * override one or more methods to modify the behavior of the backing set as desired per the <a
 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * <p><b>Warning:</b> The methods of {@code ForwardingNavigableSet} forward <i>indiscriminately</i>

 * finalization to happen. However, a call to {@code System.gc()} is specified to be no more than a
 * hint, so this technique may fail at the whim of the JDK implementation, for example if a user
 * specified the JVM flag {@code -XX:+DisableExplicitGC}. But in practice, it works very well for
 * ordinary tests.
 *

   * this implementation.
   *
   * @since 7.0
   */
  protected Iterator<E> standardIterator() {
    return listIterator();
  }

  /**
   * A sensible default implementation of {@link #listIterator()}, in terms of {@link
   * #listIterator(int)}. If you override {@link #listIterator(int)}, you may wish to override

        important to us to keep Guava as easy to use and understand as we can. That means boiling
        features down to compact but powerful abstractions, and controlling feature bloat carefully.


        Guava's main yardstick for evaluating proposed features can be summed up as [utility times
        ubiquity](https://github.com/google/guava/wiki/PhilosophyExplained#utility-times-ubiquity).

 * {@link #submitAsync} that submitted those tasks had.
 *
 * <p>This class has limited support for cancellation and other "early completions":
 *
 * <ul>
 *   <li>While calls to {@code submit} and {@code submitAsync} return a {@code Future} that can be
 *       cancelled, cancellation never propagates to a task that has started to run -- neither to

   *
   * @param executor Executor to use to dispatch events. It is the caller's responsibility to shut
   *     down the executor after the last event has been posted to this event bus.
   * @param subscriberExceptionHandler Handler used to handle exceptions thrown from subscribers.
   *     See {@link SubscriberExceptionHandler} for more information.
   * @since 16.0
   */

   * close or flush either object.
   *
   * @param from the object to read from
   * @param to the object to write to
   * @return the number of characters copied
   * @throws IOException if an I/O error occurs
   */
  @CanIgnoreReturnValue
  public static long copy(Readable from, Appendable to) throws IOException {
    // The most common case is that from is a Reader (like InputStreamReader or StringReader) so