@Override
  public int add(E element, int occurrences) {
    checkIsE(element);
    checkNonnegative(occurrences, "occurrences");
    if (occurrences == 0) {
      return count(element);
    }
    int index = element.ordinal();
    int oldCount = counts[index];
    long newCount = (long) oldCount + occurrences;
    checkArgument(newCount <= Integer.MAX_VALUE, "too many occurrences: %s", newCount);

   *     Integer#MAX_VALUE} occurrences of {@code element} in this multiset.
   */
  @CanIgnoreReturnValue
  @Override
  public final int add(@ParametricNullness E element, int occurrences) {
    if (occurrences == 0) {
      return count(element);
    }
    checkArgument(occurrences > 0, "occurrences cannot be negative: %s", occurrences);
    int entryIndex = backingMap.indexOf(element);

    }

    @Override
    public int add(E element, int occurrences) {
      checkArgument(occurrences >= 0);
      Integer frequency = backingMap.getOrDefault(element, 0);
      if (occurrences == 0) {
        return frequency;
      }
      checkArgument(occurrences <= Integer.MAX_VALUE - frequency);
      backingMap.put(element, frequency + occurrences);
      return frequency;
    }

    @Override

   * words, for the default {@code expectContents()} implementation, the number of occurrences of
   * each given element has increased by one since the test collection was created, and the number
   * of occurrences of all other elements has not changed.
   *
   * <p>Note: This means that a test like the following will fail if {@code collection} is a {@code
   * Set}:

/**
 * A {@code Multiset} implementation with predictable iteration order. Its iterator orders elements
 * according to when the first occurrence of the element was added. When the multiset contains
 * multiple instances of an element, those instances are consecutive in the iteration order. If all
 * occurrences of an element are removed, after which that element is added to the multiset, the
 * element will appear at the end of the iteration.
 *

  @Override
  public int add(@ParametricNullness E element, int occurrences) {
    throw new UnsupportedOperationException();
  }

  @CanIgnoreReturnValue
  @Override
  public final boolean remove(@Nullable Object element) {
    return remove(element, 1) > 0;
  }

  @CanIgnoreReturnValue
  @Override
  public int remove(@Nullable Object element, int occurrences) {
    throw new UnsupportedOperationException();
  }

/**
 * A {@code Multiset} implementation with predictable iteration order. Its iterator orders elements
 * according to when the first occurrence of the element was added. When the multiset contains
 * multiple instances of an element, those instances are consecutive in the iteration order. If all
 * occurrences of an element are removed, after which that element is added to the multiset, the
 * element will appear at the end of the iteration.
 *

import org.jspecify.annotations.Nullable;
import org.junit.Ignore;

/**
 * Tester to make sure the {@code iterator().remove()} implementation of {@code Multiset} works when
 * there are multiple occurrences of elements.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")

import org.jspecify.annotations.Nullable;
import org.junit.Ignore;

/**
 * Tester to make sure the {@code iterator().remove()} implementation of {@code Multiset} works when
 * there are multiple occurrences of elements.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")

    E[] array = createSamplesArray();
    array[getNumElements() / 2] = e0();
    collection = getSubjectGenerator().create(array);
    assertEquals(
        "lastIndexOf(duplicate) should return index of last occurrence",
        getNumElements() / 2,
        getList().lastIndexOf(e0()));
  }