}
    return ImmutableEnumMap.asImmutable(enumMap);
  }

  /**
   * Returns a {@link Collector} that accumulates elements into an {@code ImmutableMap} whose keys
   * and values are the result of applying the provided mapping functions to the input elements. The
   * resulting implementation is specialized for enum key types. The returned map and its views will
   * iterate over keys in their enum definition order, not encounter order.
   *

            /*
             * This test relies on behavior that's unspecified but currently
             * guaranteed by the implementation: Cancellation of inputs is
             * performed in the order they were provided to the constructor. Verify
             * that as a sanity check:
             */
            assertFalse(future2.isCancelled());
            // Now attempt to trigger the exception:
            future2.set(DATA2);

            /*
             * This test relies on behavior that's unspecified but currently
             * guaranteed by the implementation: Cancellation of inputs is
             * performed in the order they were provided to the constructor. Verify
             * that as a sanity check:
             */
            assertFalse(future2.isCancelled());
            // Now attempt to trigger the exception:
            future2.set(DATA2);

    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();

    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();