public void testSet_replacingNull() {
    E[] elements = createSamplesArray();
    int i = aValidIndex();
    elements[i] = null;
    collection = getSubjectGenerator().create(elements);

    doTestSet(e3());
  }

  private void doTestSet(E newValue) {
    int index = aValidIndex();
    E initialValue = getList().get(index);
    assertEquals(
        "set(i, x) should return the old element at position i.",
        initialValue,

public class MultisetReadsTester<E> extends AbstractMultisetTester<E> {

  @CollectionSize.Require(absent = ZERO)
  public void testElementSet_contains() {
    assertTrue(
        "multiset.elementSet().contains(present) returned false",
        getMultiset().elementSet().contains(e0()));
  }

  @CollectionSize.Require(absent = ZERO)
  public void testEntrySet_contains() {
    assertTrue(
        "multiset.entrySet() didn't contain [present, 1]",

public class MultisetReadsTester<E> extends AbstractMultisetTester<E> {

  @CollectionSize.Require(absent = ZERO)
  public void testElementSet_contains() {
    assertTrue(
        "multiset.elementSet().contains(present) returned false",
        getMultiset().elementSet().contains(e0()));
  }

  @CollectionSize.Require(absent = ZERO)
  public void testEntrySet_contains() {
    assertTrue(
        "multiset.entrySet() didn't contain [present, 1]",

    public int count(@Nullable Object element) {
      for (Entry<E> entry : entrySet()) {
        if (Objects.equal(entry.getElement(), element)) {
          return entry.getCount();
        }
      }
      return 0;
    }

    @Override
    public int add(E element, int occurrences) {
      checkArgument(occurrences >= 0);
      Integer frequency = backingMap.get(element);
      if (frequency == null) {

  }

  /**
   * Reverses the elements of {@code array}. This is equivalent to {@code
   * Collections.reverse(Bytes.asList(array))}, but is likely to be more efficient.
   *
   * @since 23.1
   */
  public static void reverse(byte[] array) {
    checkNotNull(array);
    reverse(array, 0, array.length);
  }

  /**

    ms.add("b", 2);
    ms.add("c");
    assertThat(ms.elementSet()).containsExactly("a", "b", "c").inOrder();
    ms.remove("b");
    assertThat(ms.elementSet()).containsExactly("a", "b", "c").inOrder();
    ms.add("b");
    assertThat(ms.elementSet()).containsExactly("a", "b", "c").inOrder();
    ms.remove("b", 2);
    ms.add("b");
    assertThat(ms.elementSet()).containsExactly("a", "c", "b").inOrder();
  }

   * support concurrent multisets whose content may change while the method is running.
   *
   * <p>The serialized output consists of the number of distinct elements, the first element, its
   * count, the second element, its count, and so on.
   */
  static <E extends @Nullable Object> void writeMultiset(
      Multiset<E> multiset, ObjectOutputStream stream) throws IOException {

  private static final class PickyIterable<E> implements Iterable<E> {
    final List<E> elements;
    int modCount = 0;

    PickyIterable(E... elements) {
      this.elements = new ArrayList<E>(asList(elements));
    }

    @Override
    public Iterator<E> iterator() {
      return new PickyIterator();
    }

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Creates queues, containing sample elements, to be tested.
 *
 * @author Jared Levy
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public interface TestQueueGenerator<E extends @Nullable Object> extends TestCollectionGenerator<E> {
  @Override
  Queue<E> create(Object... elements);

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Creates sets, containing sample elements, to be tested.
 *
 * @author Kevin Bourrillion
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public interface TestListGenerator<E extends @Nullable Object> extends TestCollectionGenerator<E> {
  @Override
  List<E> create(Object... elements);