@CheckForNull
  public E peekLast() {
    return isEmpty() ? null : elementData(getMaxElementIndex());
  }

  /**
   * Removes the element at position {@code index}.
   *
   * <p>Normally this method leaves the elements at up to {@code index - 1}, inclusive, untouched.
   * Under these circumstances, it returns {@code null}.
   *
   * <p>Occasionally, in order to maintain the heap invariant, it must swap a later element of the

    return s.charAt(rand.nextInt(s.length()));
  }

  /**
   * Provides samples on a random distribution derived from the web.
   *
   * <p>Adapted from data provided by Mark Davis.
   *
   * @author Christopher Swenson
   */
  static class CharSamples {

    static {
      populateProb1();
      populateProb2();
      populateChars1();
      populateChars2();
    }

    // (b) Waiting for the single guard to become satisfied.
    // (c) Occupying the monitor and awaiting the tearDownLatch.
    //
    // Except for (c), every thread should occupy the monitor very briefly, and every thread leaves
    // the monitor with the guard satisfied. Therefore as soon as tearDownLatch is triggered, we
    // should be able to enter the monitor, and then we set the guard to satisfied for the benefit

    //     imagine a line separating the first block from the second, we can proceed by exchanging
    //     the smaller of these blocks with the far end of the other one. That leaves us with a
    //     smaller version of the same problem.
    //     Say we are rotating abcdefgh by 5. We start with abcde|fgh. The smaller block is [fgh]:

   *
   * <p><b>Comparison to {@code java.util.Optional}:</b> this class leaves the specific choice of
   * hash code unspecified, unlike the Java 8+ equivalent.
   */
  @Override
  public abstract int hashCode();

  /**
   * Returns a string representation for this instance.
   *
   * <p><b>Comparison to {@code java.util.Optional}:</b> this class leaves the specific string

seemed to rise like a stalk out of a sea of green leaves that lay
far below her.

  `What CAN all that green stuff be?' said Alice.  `And where
HAVE my shoulders got to?  And oh, my poor hands, how is it I
can't see you?'  She was moving them about as she spoke, but no
result seemed to follow, except a little shaking among the
distant green leaves.

  As there seemed to be no chance of getting her hands up to her

    return s.charAt(rand.nextInt(s.length()));
  }

  /**
   * Provides samples on a random distribution derived from the web.
   *
   * <p>Adapted from data provided by Mark Davis.
   *
   * @author Christopher Swenson
   */
  static class CharSamples {

    static {
      populateProb1();
      populateProb2();
      populateChars1();
      populateChars2();
    }

   *
   * <p>Why <i>not</i> just add {@code SuppressWarnings}? The problem is that this method is
   * typically useful for {@code return} statements. That leaves the code with two options: Either
   * add the suppression to the whole method (which turns off checking for a large section of code),
   * or extract a variable, and put the suppression on that. However, a local variable typically

              <logLevel>${gwt.logLevel}</logLevel>
              <mode>htmlunit</mode>
              <htmlunit>FF38</htmlunit>
              <productionMode>true</productionMode>
              <!-- Fix OutOfMemoryError under Travis. -->
              <extraJvmArgs>-Xms3500m -Xmx3500m -Xss1024k</extraJvmArgs>
              <sourceLevel>1.8</sourceLevel>