Sets.symmetricDifference(friends, enemies).copyInto(new HashSet<String>());

    enemies.add("Dave");
    assertEquals(3, symmetricDifferenceFriendsFirst.size());
    assertEquals(4, immut.size());
    assertEquals(4, mut.size());

    immut = Sets.symmetricDifference(enemies, friends).immutableCopy();
    mut = Sets.symmetricDifference(enemies, friends).copyInto(new HashSet<String>());
    friends.add("Harry");

        Sets.symmetricDifference(friends, enemies).copyInto(new HashSet<String>());

    enemies.add("Dave");
    assertEquals(3, symmetricDifferenceFriendsFirst.size());
    assertEquals(4, immut.size());
    assertEquals(4, mut.size());

    immut = Sets.symmetricDifference(enemies, friends).immutableCopy();
    mut = Sets.symmetricDifference(enemies, friends).copyInto(new HashSet<String>());
    friends.add("Harry");

    assertThat(fluent(1, 3, 5).copyInto(Lists.newArrayList(1, 2)))
        .containsExactly(1, 2, 1, 3, 5)
        .inOrder();
  }

  public void testCopyInto_Set() {
    assertThat(fluent(1, 3, 5).copyInto(Sets.newHashSet(1, 2))).containsExactly(1, 2, 3, 5);
  }

  public void testCopyInto_SetAllDuplicates() {
    assertThat(fluent(1, 3, 5).copyInto(Sets.newHashSet(1, 2, 3, 5))).containsExactly(1, 2, 3, 5);

    assertThat(fluent(1, 3, 5).copyInto(Lists.newArrayList(1, 2)))
        .containsExactly(1, 2, 1, 3, 5)
        .inOrder();
  }

  public void testCopyInto_Set() {
    assertThat(fluent(1, 3, 5).copyInto(Sets.newHashSet(1, 2))).containsExactly(1, 2, 3, 5);
  }

  public void testCopyInto_SetAllDuplicates() {
    assertThat(fluent(1, 3, 5).copyInto(Sets.newHashSet(1, 2, 3, 5))).containsExactly(1, 2, 3, 5);

  //      after: { 11, 11, 22, 22, 33, 33, 00, 00, 00, 00, 00, 00, 77, 77, 88, 88 }
  //
  if (b != address.size) {
    if (compress == -1) return null // Address didn't have compression or enough groups.
    address.copyInto(address, address.size - (b - compress), compress, b)
    address.fill(0.toByte(), compress, compress + (address.size - b))
  }

  return address
}

   *
   * @param collection the collection to copy elements to
   * @return {@code collection}, for convenience
   * @since 14.0
   */
  @CanIgnoreReturnValue
  public final <C extends Collection<? super E>> C copyInto(C collection) {
    checkNotNull(collection);
    Iterable<E> iterable = getDelegate();
    if (iterable instanceof Collection) {
      collection.addAll((Collection<E>) iterable);
    } else {

   *
   * @param collection the collection to copy elements to
   * @return {@code collection}, for convenience
   * @since 14.0
   */
  @CanIgnoreReturnValue
  public final <C extends Collection<? super E>> C copyInto(C collection) {
    checkNotNull(collection);
    Iterable<E> iterable = getDelegate();
    if (iterable instanceof Collection) {
      collection.addAll((Collection<E>) iterable);
    } else {

    assertFalse(writer.closed());
    source.copyTo(writer);
    assertFalse(writer.closed());
  }

  public void testClosesOnErrors_copyingToCharSinkThatThrows() {
    for (TestOption option : EnumSet.of(OPEN_THROWS, WRITE_THROWS, CLOSE_THROWS)) {
      TestCharSource okSource = new TestCharSource(STRING);
      assertThrows(IOException.class, () -> okSource.copyTo(new TestCharSink(option)));

    assertFalse(writer.closed());
    source.copyTo(writer);
    assertFalse(writer.closed());
  }

  public void testClosesOnErrors_copyingToCharSinkThatThrows() {
    for (TestOption option : EnumSet.of(OPEN_THROWS, WRITE_THROWS, CLOSE_THROWS)) {
      TestCharSource okSource = new TestCharSource(STRING);
      assertThrows(IOException.class, () -> okSource.copyTo(new TestCharSink(option)));

    assertFalse(out.closed());
    source.copyTo(out);
    assertFalse(out.closed());
  }

  public void testClosesOnErrors_copyingToByteSinkThatThrows() {
    for (TestOption option : EnumSet.of(OPEN_THROWS, WRITE_THROWS, CLOSE_THROWS)) {
      TestByteSource okSource = new TestByteSource(bytes);
      assertThrows(IOException.class, () -> okSource.copyTo(new TestByteSink(option)));