*
   * <p>This method always throws an exception. The {@code RuntimeException} return type allows
   * client code to signal to the compiler that statements after the call are unreachable. Example
   * usage:
   *
   * <pre>
   * T doSomething() {
   *   try {
   *     return someMethodThatCouldThrowAnything();
   *   } catch (IKnowWhatToDoWithThisException e) {

   *
   * <p>This method always throws an exception. The {@code RuntimeException} return type allows
   * client code to signal to the compiler that statements after the call are unreachable. Example
   * usage:
   *
   * <pre>
   * T doSomething() {
   *   try {
   *     return someMethodThatCouldThrowAnything();
   *   } catch (IKnowWhatToDoWithThisException e) {

    long guess = (long) Math.sqrt((double) x);
    // Note: guess is always <= FLOOR_SQRT_MAX_LONG.
    long guessSquared = guess * guess;
    // Note (2013-2-26): benchmarks indicate that, inscrutably enough, using if statements is
    // faster here than using lessThanBranchFree.
    switch (mode) {
      case UNNECESSARY:
        checkRoundingUnnecessary(guessSquared == x);
        return guess;
      case FLOOR:
      case DOWN:

        getRawType().isAssignableFrom(subclass), "%s isn't a subclass of %s", subclass, this);
    Type resolvedTypeArgs = resolveTypeArgsForSubclass(subclass);
    @SuppressWarnings("unchecked") // guarded by the isAssignableFrom() statement above
    TypeToken<? extends T> subtype = (TypeToken<? extends T>) of(resolvedTypeArgs);
    checkArgument(
        subtype.isSubtypeOf(this), "%s does not appear to be a subtype of %s", subtype, this);
    return subtype;

   * without having to add {@code @SuppressWarnings}, the code can call this method.
   *
   * <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),

   * elements left in the iteration.
   *
   * @return {@code null}; a convenience so your {@code computeNext} implementation can use the
   *     simple statement {@code return endOfData();}
   */
  @CanIgnoreReturnValue
  @CheckForNull
  protected final T endOfData() {
    state = State.DONE;
    return null;
  }

  @Override

   * without having to add {@code @SuppressWarnings}, the code can call this method.
   *
   * <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),

          while (top.hasNext()) {
            N element = top.next();
            // requireNonNull is safe because horizon contains only graph nodes.
            /*
             * TODO(cpovirk): Replace these two statements with one (`N element =
             * requireNonNull(top.next())`) once our checker supports it.
             *
             * (The problem is likely

   * Collections#reverseOrder(Comparator)}.
   *
   * <p><b>Java 8+ users:</b> Use {@code thisComparator.reversed()} instead.
   */
  // type parameter <S> lets us avoid the extra <String> in statements like:
  // Ordering<String> o = Ordering.<String>natural().reverse();
  @GwtCompatible(serializable = true)
  public <S extends T> Ordering<S> reverse() {
    return new ReverseOrdering<>(this);
  }

  /**

  interface Y {}

  static class A implements X, Y {}

  static class B implements X, Y {}

  /**
   * This test passes if the {@code concat(…).filter(…).filter(…)} statement at the end compiles.
   * That statement compiles only if {@link FluentIterable#concat concat(aIterable, bIterable)}
   * returns a {@link FluentIterable} of elements of an anonymous type whose supertypes are the <a