*   <li>awaits executor service termination for half of the specified timeout.
   *   <li>if the timeout expires, it calls {@link ExecutorService#shutdownNow()}, cancelling
   *       pending tasks and interrupting running tasks.
   *   <li>awaits executor service termination for the other half of the specified timeout.
   * </ol>
   *

   * characters which constitute a machine-sensible address or routing information. Such a sequence
   * is referred to as the "heading." An STX character has the effect of terminating a heading.
   *
   * @since 8.0
   */
  public static final byte SOH = 1;

  /**
   * Start of Text: A communication control character which precedes a sequence of characters that

   *
   * <p>Providing a graph to be traversed for which there is more than one path from the start
   * node(s) to any node may lead to:
   *
   * <ul>
   *   <li>Traversal not terminating (if the graph has cycles)
   *   <li>Nodes being visited multiple times (if multiple paths exist from any start node to any
   *       node reachable from any start node)
   * </ul>
   *

   * characters which constitute a machine-sensible address or routing information. Such a sequence
   * is referred to as the "heading." An STX character has the effect of terminating a heading.
   *
   * @since 8.0
   */
  public static final byte SOH = 1;

  /**
   * Start of Text: A communication control character which precedes a sequence of characters that

   *
   * <p>Although all tasks are immediately executed in the thread that submitted the task, this
   * {@code ExecutorService} imposes a small locking overhead on each task submission in order to
   * implement shutdown and termination behavior.
   *
   * <p>Because of the nature of single-thread execution, the methods {@code scheduleAtFixedRate}
   * and {@code scheduleWithFixedDelay} are not supported by this class and will throw an

      else // too short to sleep
      Thread.yield();
      long d = ns - (System.nanoTime() - startTime);
      if (d > 0L) millis = d / (1000 * 1000);
      else break;
    }
  }

  /** Waits out termination of a thread pool or fails doing so. */
  void joinPool(ExecutorService exec) {
    try {
      exec.shutdown();
      assertTrue(
          "ExecutorService did not terminate in a timely manner",

 * with the abstract {@link #execute execute(Runnable)} method.
 *
 * <p>In addition to {@link #execute}, subclasses must implement all methods related to shutdown and
 * termination.
 *
 * @author Chris Povirk
 * @since 14.0
 */
@CheckReturnValue
@GwtIncompatible
@J2ktIncompatible
@ElementTypesAreNonnullByDefault

    return asCharSource(url, charset).readLines(callback);
  }

  /**
   * Reads all of the lines from a URL. The lines do not include line-termination characters, but do
   * include other leading and trailing whitespace.
   *
   * <p>This method returns a mutable {@code List}. For an {@code ImmutableList}, use {@code

      else // too short to sleep
      Thread.yield();
      long d = ns - (System.nanoTime() - startTime);
      if (d > 0L) millis = d / (1000 * 1000);
      else break;
    }
  }

  /** Waits out termination of a thread pool or fails doing so. */
  void joinPool(ExecutorService exec) {
    try {
      exec.shutdown();
      assertTrue(
          "ExecutorService did not terminate in a timely manner",

   * text that is terminated by (but does not include) one of {@code \r\n}, {@code \r} or {@code
   * \n}. If the source's content does not end in a line termination sequence, it is treated as if
   * it does.
   *
   * @throws IOException if an I/O error occurs while reading from this source
   */
  @CheckForNull
  public String readFirstLine() throws IOException {