* </ul>
   *
   * <p>This method is suitable for the common use case of dividing work among buckets that meet the
   * following conditions:
   *
   * <ul>
   *   <li>You want to assign the same fraction of inputs to each bucket.
   *   <li>When you reduce the number of buckets, you can accept that the most recently added

   * Returns the innermost cause of {@code throwable}. The first throwable in a chain provides
   * context from when the error or exception was initially detected. Example usage:
   *
   * <pre>
   * assertEquals("Unable to assign a customer id", Throwables.getRootCause(e).getMessage());
   * </pre>
   *
   * @throws IllegalArgumentException if there is a loop in the causal chain
   */
  public static Throwable getRootCause(Throwable throwable) {

   * Returns the innermost cause of {@code throwable}. The first throwable in a chain provides
   * context from when the error or exception was initially detected. Example usage:
   *
   * <pre>
   * assertEquals("Unable to assign a customer id", Throwables.getRootCause(e).getMessage());
   * </pre>
   *
   * @throws IllegalArgumentException if there is a loop in the causal chain
   */
  public static Throwable getRootCause(Throwable throwable) {

   * elements.
   *
   * <p>To cycle over the elements {@code n} times, use the following: {@code
   * Iterables.concat(Collections.nCopies(n, Arrays.asList(elements)))}
   *
   * <p><b>Java 8+ users:</b> If passing a single element {@code e}, the {@code Stream} equivalent
   * of this method is {@code Stream.generate(() -> e)}. Otherwise, put the elements in a collection

   *
   * @param formal The type whose type variables or itself is mapped to other type(s). It's almost
   *     always a bug if {@code formal} isn't a type variable and contains no type variable. Make
   *     sure you are passing the two parameters in the right order.
   * @param actual The type that the formal type variable(s) are mapped to. It can be or contain yet
   *     other type variables, in which case these type variables will be further resolved if

 * worst case time complexity of O(N^2). You are extremely unlikely to hit this quadratic case on
 * randomly ordered data (the probability decreases faster than exponentially in N), but if you are
 * passing in unsanitized user data then a malicious user could force it. A light shuffle of the
 * data using an unpredictable seed should normally be enough to thwart this attack.
 *

   * in which case the signal is a no-op, and the bigger-picture signal is lost unless interrupted
   * threads take special action by participating in the signal-passing game.
   */

  /*
   * Timeout handling is intricate, especially given our ambitious goals:
   * - Avoid underflow and overflow of timeout values when specified timeouts are close to

 * reasonable and it will be fine.
 *
 * <ul>
 *   <li>If checking whether the <i>caller</i> has violated your method or constructor's contract
 *       (such as by passing an invalid argument), use the utilities of the {@link Preconditions}
 *       class instead.
 *   <li>If checking an <i>impossible</i> condition (which <i>cannot</i> happen unless your own

  }

  public void testLimit_illegalArgument() {
    try {
      FluentIterable<String> unused =
          FluentIterable.from(Lists.newArrayList("a", "b", "c")).limit(-1);
      fail("Passing negative number to limit(...) method should throw IllegalArgumentException");
    } catch (IllegalArgumentException expected) {
    }
  }

  public void testIsEmpty() {

                (v1, v2) -> {
                  throw new IllegalArgumentException("Multiple values for key: " + v1 + ", " + v2);
                }),
        (accum, t) -> {
          /*
           * We assign these to variables before calling checkNotNull to work around a bug in our
           * nullness checker.
           */
          K key = keyFunction.apply(t);
          V newValue = valueFunction.apply(t);