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();

    teststring = newTestString(new Random(1), bitSet, percentMatching);
  }

  @Benchmark
  public int countIn(int reps) {
    int result = 0;
    CharMatcher matcher = this.matcher;
    String teststring = this.teststring;
    for (int i = 0; i < reps; i++) {
      result += matcher.countIn(teststring);
    }
    return result;
  }

  @Benchmark
  public int collapseFrom(int reps) {
    int result = 0;

    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;
  }

  /**

      }
      return textToNumericFormatV4(ipString);
    }
    return null;
  }

  private static byte @Nullable [] textToNumericFormatV4(String ipString) {
    if (IPV4_DELIMITER_MATCHER.countIn(ipString) + 1 != IPV4_PART_COUNT) {
      return null; // Wrong number of parts
    }

    byte[] bytes = new byte[IPV4_PART_COUNT];
    int start = 0;
    // Iterate through the parts of the ip string.

      }
      return textToNumericFormatV4(ipString);
    }
    return null;
  }

  private static byte @Nullable [] textToNumericFormatV4(String ipString) {
    if (IPV4_DELIMITER_MATCHER.countIn(ipString) + 1 != IPV4_PART_COUNT) {
      return null; // Wrong number of parts
    }

    byte[] bytes = new byte[IPV4_PART_COUNT];
    int start = 0;
    // Iterate through the parts of the ip string.

import java.io.Serializable;
import org.jspecify.annotations.Nullable;

/**
 * A mutable value of type {@code int}, for multisets to use in tracking counts of values.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
final class Count implements Serializable {
  private int value;

  Count(int value) {
    this.value = value;
  }

  public int get() {
    return value;
  }

  public void add(int delta) {

    return multiset(ImmutableMap.of(value1, count1, value2, count2));
  }

  private static <T> ImmutableMultiset<T> multiset(Map<T, Integer> counts) {
    ImmutableMultiset.Builder<T> builder = ImmutableMultiset.builder();
    for (Entry<T, Integer> entry : counts.entrySet()) {
      builder.addCopies(entry.getKey(), entry.getValue());
    }
    return builder.build();
  }

    return multiset(ImmutableMap.of(value1, count1, value2, count2));
  }

  private static <T> ImmutableMultiset<T> multiset(Map<T, Integer> counts) {
    ImmutableMultiset.Builder<T> builder = ImmutableMultiset.builder();
    for (Entry<T, Integer> entry : counts.entrySet()) {
      builder.addCopies(entry.getKey(), entry.getValue());
    }
    return builder.build();
  }

import java.io.IOException;
import java.io.OutputStream;

/**
 * An OutputStream that counts the number of bytes written.
 *
 * @author Chris Nokleberg
 * @since 1.0
 */
@J2ktIncompatible
@GwtIncompatible
public final class CountingOutputStream extends FilterOutputStream {

  private long count;

  /**
   * Wraps another output stream, counting the number of bytes written.
   *
   * @param out the output stream to be wrapped