assertThat(Multisets.difference(ms1, ms2)).containsExactly("a", "b");
  }

  public void testDifferenceWithRemovedElement() {
    Multiset<String> ms1 = HashMultiset.create(Arrays.asList("a", "b", "a"));
    Multiset<String> ms2 = HashMultiset.create(Arrays.asList("b"));
    assertThat(Multisets.difference(ms1, ms2)).containsExactly("a", "a");
  }

    Set<String> enemies = Sets.newHashSet("Dick", "Harry", "Tom");

    Set<String> goodFriends = Sets.difference(friends, enemies);
    assertEquals(2, goodFriends.size());

    ImmutableSet<String> immut = Sets.difference(friends, enemies).immutableCopy();
    HashSet<String> mut = Sets.difference(friends, enemies).copyInto(new HashSet<String>());

    enemies.add("Dave");
    assertEquals(1, goodFriends.size());

    Set<String> enemies = Sets.newHashSet("Dick", "Harry", "Tom");

    Set<String> goodFriends = Sets.difference(friends, enemies);
    assertEquals(2, goodFriends.size());

    ImmutableSet<String> immut = Sets.difference(friends, enemies).immutableCopy();
    HashSet<String> mut = Sets.difference(friends, enemies).copyInto(new HashSet<String>());

    enemies.add("Dave");
    assertEquals(1, goodFriends.size());

  }

  public void testOneSecondBurst() {
    RateLimiter limiter = RateLimiter.create(5.0, stopwatch);
    stopwatch.sleepMillis(1000); // max capacity reached
    stopwatch.sleepMillis(1000); // this makes no difference
    limiter.acquire(1); // R0.00, since it's the first request

    limiter.acquire(1); // R0.00, from capacity
    limiter.acquire(3); // R0.00, from capacity

    assertThat(Multisets.difference(ms1, ms2)).containsExactly("a", "b");
  }

  public void testDifferenceWithRemovedElement() {
    Multiset<String> ms1 = HashMultiset.create(Arrays.asList("a", "b", "a"));
    Multiset<String> ms2 = HashMultiset.create(Arrays.asList("b"));
    assertThat(Multisets.difference(ms1, ms2)).containsExactly("a", "a");
  }

  }

  public void testOneSecondBurst() {
    RateLimiter limiter = RateLimiter.create(5.0, stopwatch);
    stopwatch.sleepMillis(1000); // max capacity reached
    stopwatch.sleepMillis(1000); // this makes no difference
    limiter.acquire(1); // R0.00, since it's the first request

    limiter.acquire(1); // R0.00, from capacity
    limiter.acquire(3); // R0.00, from capacity

   *
   * <p>Results are undefined if {@code multiset1} and {@code multiset2} are based on different
   * equivalence relations (as {@code HashMultiset} and {@code TreeMultiset} are).
   *
   * @since 14.0
   */
  public static <E extends @Nullable Object> Multiset<E> difference(
      final Multiset<E> multiset1, final Multiset<?> multiset2) {
    checkNotNull(multiset1);
    checkNotNull(multiset2);

  }

  /**
   * Returns a new range set consisting of the difference of this range set and {@code other}.
   *
   * <p>This is essentially the same as {@code TreeRangeSet.create(this).removeAll(other)} except it
   * returns an {@code ImmutableRangeSet}.
   *
   * @since 21.0
   */
  public ImmutableRangeSet<C> difference(RangeSet<C> other) {
    RangeSet<C> copy = TreeRangeSet.create(this);

  }

  /**
   * Returns a new range set consisting of the difference of this range set and {@code other}.
   *
   * <p>This is essentially the same as {@code TreeRangeSet.create(this).removeAll(other)} except it
   * returns an {@code ImmutableRangeSet}.
   *
   * @since 21.0
   */
  public ImmutableRangeSet<C> difference(RangeSet<C> other) {
    RangeSet<C> copy = TreeRangeSet.create(this);

      // If a and b have different signs or a has the same sign as the result then there was no
      // overflow, return.
      return naiveSum;
    }
    // we did over/under flow, if the sign is negative we should return MAX otherwise MIN
    return Long.MAX_VALUE + ((naiveSum >>> (Long.SIZE - 1)) ^ 1);
  }

  /**