assertEquals("", matcher.removeFrom(""));
    assertEquals("", matcher.replaceFrom("", 'z'));
    assertEquals("", matcher.replaceFrom("", "ZZ"));
    assertEquals("", matcher.trimFrom(""));
    assertEquals(0, matcher.countIn(""));
  }

  @J2ktIncompatible
  @GwtIncompatible // NullPointerTester
  private static void doTestNull(CharMatcher matcher) throws Exception {
    NullPointerTester tester = new NullPointerTester();

    assertEquals("", matcher.removeFrom(""));
    assertEquals("", matcher.replaceFrom("", 'z'));
    assertEquals("", matcher.replaceFrom("", "ZZ"));
    assertEquals("", matcher.trimFrom(""));
    assertEquals(0, matcher.countIn(""));
  }

  @J2ktIncompatible
  @GwtIncompatible // NullPointerTester
  private static void doTestNull(CharMatcher matcher) throws Exception {
    NullPointerTester tester = new NullPointerTester();

   *
   * <p>Counts 2 per supplementary character, such as for {@link #whitespace}().{@link #negate}().
   */
  public int countIn(CharSequence sequence) {
    int count = 0;
    for (int i = 0; i < sequence.length(); i++) {
      if (matches(sequence.charAt(i))) {
        count++;
      }
    }
    return count;
  }

  /**

            count = new AtomicInteger(1);
        }

        /**
         * Increments the reference count for this statistics object.
         *
         * @return the new reference count after incrementing
         */
        public int increment() {
            return count.incrementAndGet();
        }

        /**
         * Decrements the reference count for this statistics object.
         *

  @Override
  public int setCount(E element, int count) {
    checkIsE(element);
    checkNonnegative(count, "count");
    int index = element.ordinal();
    int oldCount = counts[index];
    counts[index] = count;
    size += count - oldCount;
    if (oldCount == 0 && count > 0) {
      distinctElements++;
    } else if (oldCount > 0 && count == 0) {
      distinctElements--;
    }
    return oldCount;

      void doIt(ImmutableDoubleArray.Builder builder, AtomicInteger counter) {
        builder.add(counter.getAndIncrement());
      }
    },
    ADD_ARRAY {
      @Override
      void doIt(ImmutableDoubleArray.Builder builder, AtomicInteger counter) {
        double[] array = new double[random.nextInt(10)];
        for (int i = 0; i < array.length; i++) {
          array[i] = counter.getAndIncrement();
        }

     * desired count.
     *
     * @param element the element to add or remove occurrences of
     * @param count the desired count of the element in this multiset
     * @return this {@code Builder} object
     * @throws NullPointerException if {@code element} is null
     * @throws IllegalArgumentException if {@code count} is negative
     */
    @CanIgnoreReturnValue

      void doIt(ImmutableIntArray.Builder builder, AtomicInteger counter) {
        builder.add(counter.getAndIncrement());
      }
    },
    ADD_ARRAY {
      @Override
      void doIt(ImmutableIntArray.Builder builder, AtomicInteger counter) {
        int[] array = new int[random.nextInt(10)];
        for (int i = 0; i < array.length; i++) {
          array[i] = counter.getAndIncrement();
        }
        builder.addAll(array);

      void doIt(ImmutableLongArray.Builder builder, AtomicLong counter) {
        builder.add(counter.getAndIncrement());
      }
    },
    ADD_ARRAY {
      @Override
      void doIt(ImmutableLongArray.Builder builder, AtomicLong counter) {
        long[] array = new long[random.nextInt(10)];
        for (int i = 0; i < array.length; i++) {
          array[i] = counter.getAndIncrement();
        }
        builder.addAll(array);

      void doIt(ImmutableDoubleArray.Builder builder, AtomicInteger counter) {
        builder.add(counter.getAndIncrement());
      }
    },
    ADD_ARRAY {
      @Override
      void doIt(ImmutableDoubleArray.Builder builder, AtomicInteger counter) {
        double[] array = new double[random.nextInt(10)];
        for (int i = 0; i < array.length; i++) {
          array[i] = counter.getAndIncrement();
        }