final Stack<E> previousElements = new Stack<>();

    /**
     * {@link #nextElements} if {@code next()} was called more recently then {@code previous},
     * {@link #previousElements} if the reverse is true, or -- overriding both of these -- {@code
     * null} if {@code remove()} or {@code add()} has been called more recently than either. We use
     * this to determine which stack to pop from on a call to {@code remove()} (or to pop from and

   * the first is returned.
   *
   * <p><b>Implementation note:</b> this method is invoked by the default implementations of the
   * other {@code min} overloads, so overriding it will affect their behavior.
   *
   * <p><b>Note:</b> Consider using {@code Comparators.min(a, b, thisComparator)} instead. If {@code
   * thisComparator} is {@link Ordering#natural}, then use {@code Comparators.min(a, b)}.

             'compilation to reduce the compilation time?'),
      'Eigen strong inline overridden.', 'Not overriding eigen strong inline, '
      'some compilations could take more than 20 mins.'):
    # Due to a known MSVC compiler issue
    # https://github.com/tensorflow/tensorflow/issues/10521
    # Overriding eigen strong inline speeds up the compiling of
    # conv_grad_ops_3d.cc and conv_ops_3d.cc by 20 minutes,

 *
 * @since 2.0
 */
@DoNotMock("Use ImmutableList.of or another implementation")
@GwtCompatible
@SuppressWarnings("serial") // we're overriding default serialization
// TODO(kevinb): I think we should push everything down to "BaseImmutableCollection" or something,
// just to do everything we can to emphasize the "practically an interface" nature of this class.

 *
 * @author Jared Levy
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
@SuppressWarnings("serial") // we're overriding default serialization
public abstract class ImmutableMultiset<E> extends ImmutableCollection<E> implements Multiset<E> {

  /**
   * Returns a {@code Collector} that accumulates the input elements into a new {@code

 *
 * @since 2.0
 */
@DoNotMock("Use ImmutableList.of or another implementation")
@GwtCompatible
@SuppressWarnings("serial") // we're overriding default serialization
// TODO(kevinb): I think we should push everything down to "BaseImmutableCollection" or something,
// just to do everything we can to emphasize the "practically an interface" nature of this class.

            .build();

    RangeMap<Integer, Integer> copy = TreeRangeMap.copyOf(rangeMap);

    assertEquals(rangeMap.asMapOfRanges(), copy.asMapOfRanges());
  }

  // Overriding testEquals because it seems that we get spurious failures when it things empty
  // should be unequal to empty.
  public void testEquals() {
    TreeRangeMap<Integer, Integer> empty = TreeRangeMap.create();

/**
 * A {@link Set} whose contents will never change, with many other important properties detailed at
 * {@link ImmutableCollection}.
 *
 * @since 2.0
 */
@GwtCompatible
@SuppressWarnings("serial") // we're overriding default serialization
public abstract class ImmutableSet<E> extends ImmutableCollection<E> implements Set<E> {
  // @IgnoreJRERequirement is not necessary because this compiles down to a constant.

 *
 * @author Jesse Wilson
 * @author Kevin Bourrillion
 * @since 2.0
 */
@DoNotMock("Use ImmutableMap.of or another implementation")
@GwtCompatible
@SuppressWarnings("serial") // we're overriding default serialization
public abstract class ImmutableMap<K, V> implements Map<K, V>, Serializable {

  /**
   * Returns a {@link Collector} that accumulates elements into an {@code ImmutableMap} whose keys

 *
 * @author Jesse Wilson
 * @author Kevin Bourrillion
 * @since 2.0
 */
@DoNotMock("Use ImmutableMap.of or another implementation")
@GwtCompatible
@SuppressWarnings("serial") // we're overriding default serialization
public abstract class ImmutableMap<K, V> implements Map<K, V>, Serializable {

  /**
   * Returns a {@link Collector} that accumulates elements into an {@code ImmutableMap} whose keys