BigInteger.valueOf(Long.MAX_VALUE)
          .multiply(BigInteger.valueOf(Long.MAX_VALUE))
          .divide(BigInteger.valueOf(16L))
          .doubleValue();

  /**
   * Returns a stream of a million primitive doubles. The stream is parallel, which should cause
   * {@code collect} calls to run in multithreaded mode, so testing the combiner as well as the
   * supplier and accumulator.
   */

      BigInteger.valueOf(Long.MAX_VALUE)
          .multiply(BigInteger.valueOf(Long.MAX_VALUE))
          .divide(BigInteger.valueOf(16L))
          .doubleValue();

  /**
   * Returns a stream of a million primitive doubles. The stream is parallel, which should cause
   * {@code collect} calls to run in multithreaded mode, so testing the combiner as well as the
   * supplier and accumulator.
   */

  }

  private static class SleepingRunnable implements Runnable {
    final int millis;
    volatile boolean completed;

    SleepingRunnable(int millis) {
      this.millis = millis;
    }

    @Override
    public void run() {
      try {
        Thread.sleep(millis);
      } catch (InterruptedException wontHappen) {
        throw new AssertionError();
      }

   */
  @SuppressWarnings("ThreadPriorityCheck") // TODO: b/175898629 - Consider onSpinWait?
  static void delay(long millis) throws InterruptedException {
    long startTime = System.nanoTime();
    long ns = millis * 1000 * 1000;
    for (; ; ) {
      if (millis > 0L) {
        Thread.sleep(millis);
      } else {
        // too short to sleep
        Thread.yield();
      }

   */
  @SuppressWarnings("ThreadPriorityCheck") // TODO: b/175898629 - Consider onSpinWait?
  static void delay(long millis) throws InterruptedException {
    long startTime = System.nanoTime();
    long ns = millis * 1000 * 1000;
    for (; ; ) {
      if (millis > 0L) {
        Thread.sleep(millis);
      } else {
        // too short to sleep
        Thread.yield();
      }

  }

  private static class SleepingRunnable implements Runnable {
    final int millis;
    volatile boolean completed;

    SleepingRunnable(int millis) {
      this.millis = millis;
    }

    @Override
    public void run() {
      try {
        Thread.sleep(millis);
      } catch (InterruptedException wontHappen) {
        throw new AssertionError();
      }

    LARGE(UNEXPECTED_HANG_DELAY_MILLIS * 2, (2 * UNEXPECTED_HANG_DELAY_MILLIS) + "ms"),
    MAX(Long.MAX_VALUE, "+oo");

    final long millis;
    final String label;

    Timeout(long millis, String label) {
      this.millis = millis;
      this.label = label;
    }

    @Override
    public String toString() {
      return label;
    }
  }

    LARGE(UNEXPECTED_HANG_DELAY_MILLIS * 2, (2 * UNEXPECTED_HANG_DELAY_MILLIS) + "ms"),
    MAX(Long.MAX_VALUE, "+oo");

    final long millis;
    final String label;

    Timeout(long millis, String label) {
      this.millis = millis;
      this.label = label;
    }

    @Override
    public String toString() {
      return label;
    }
  }

        long days = duration.toDays();
        long hours = duration.toHoursPart();
        long minutes = duration.toMinutesPart();
        long seconds = duration.toSecondsPart();
        long millis = duration.toMillisPart();

        if (days > 0) {
            return String.format("%d d %02d:%02d h", days, hours, minutes);
        } else if (hours > 0) {

#### A "professional" attack { #a-professional-attack }

Of course, the attackers would not try all this by hand, they would write a program to do it, possibly with thousands or millions of tests per second. And they would get just one extra correct letter at a time.