static final RegularImmutableMultiset<Object> EMPTY =
      new RegularImmutableMultiset<>(ObjectCountHashMap.create());

  final transient ObjectCountHashMap<E> contents;
  private final transient int size;

  @LazyInit private transient @Nullable ImmutableSet<E> elementSet;

  RegularImmutableMultiset(ObjectCountHashMap<E> contents) {
    this.contents = contents;
    long size = 0;

import java.util.Arrays;
import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**
 * {@code ObjectCountLinkedHashMap} is a subclass of {@code ObjectCountHashMap} with insertion
 * iteration order, and uses arrays to store key objects and count values. Comparing to using a
 * traditional {@code LinkedHashMap} implementation which stores keys and count values as map