* tolerance is implemented differently: Its implementation avoids calling this toString(Object)
     * method in the first place.)
     */
    requireNonNull(part);
    return (part instanceof CharSequence) ? (CharSequence) part : part.toString();
  }

  private static Iterable<@Nullable Object> iterable(
      @CheckForNull Object first, @CheckForNull Object second, @Nullable Object[] rest) {
    checkNotNull(rest);

  }

  @GwtIncompatible // ObjectArrays.concat(Object[], Object[], Class)
  public void testConcatWithMoreGeneralType() {
    CharSequence[] result = ObjectArrays.concat(new String[0], new String[0], CharSequence.class);
    assertEquals(CharSequence[].class, result.getClass());
  }

  public void testToArrayImpl1() {
    doTestToArrayImpl1(Lists.<Integer>newArrayList());

  private static final Appendable NASTY_APPENDABLE =
      new Appendable() {
        @Override
        public Appendable append(@Nullable CharSequence csq) throws IOException {
          throw new IOException();
        }

        @Override
        public Appendable append(@Nullable CharSequence csq, int start, int end)
            throws IOException {
          throw new IOException();
        }

        @Override

   * time and space.
   *
   * @throws IllegalArgumentException if {@code sequence} contains ill-formed UTF-16 (unpaired
   *     surrogates)
   */
  public static int encodedLength(CharSequence sequence) {
    // Warning to maintainers: this implementation is highly optimized.
    int utf16Length = sequence.length();
    int utf8Length = utf16Length;
    int i = 0;

    // This loop optimizes for pure ASCII.

 * but works with any {@link CharSequence}.
 *
 * @author Colin Decker
 */
// TODO(cgdecker): make this public? as a type, or a method in CharStreams?
@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault
final class CharSequenceReader extends Reader {

  @CheckForNull private CharSequence seq;
  private int pos;
  private int mark;

  abstract int maxDecodedSize(int chars);

  abstract int decodeTo(byte[] target, CharSequence chars) throws DecodingException;

  CharSequence trimTrailingPadding(CharSequence chars) {
    return checkNotNull(chars);
  }

  // Modified encoding generators

  /**

    target.append(c);
    return this;
  }

  @Override
  public Writer append(@CheckForNull CharSequence charSeq) throws IOException {
    checkNotClosed();
    target.append(charSeq);
    return this;
  }

  @Override
  public Writer append(@CheckForNull CharSequence charSeq, int start, int end) throws IOException {
    checkNotClosed();
    target.append(charSeq, start, end);
    return this;

   * {@link #splitToList(CharSequence)}. Java 8+ users may prefer {@link #splitToStream} instead.
   *
   * @param sequence the sequence of characters to split
   * @return an iteration over the segments split from the parameter
   */
  public Iterable<String> split(final CharSequence sequence) {
    checkNotNull(sequence);

    return new Iterable<String>() {

  private final Pattern pattern;

  JdkPattern(Pattern pattern) {
    this.pattern = Preconditions.checkNotNull(pattern);
  }

  @Override
  public CommonMatcher matcher(CharSequence t) {
    return new JdkMatcher(pattern.matcher(t));
  }

  @Override
  public String pattern() {
    return pattern.pattern();
  }

  @Override
  public int flags() {
    return pattern.flags();

    StringBuilder result = new StringBuilder();

    @Override
    public Appendable append(CharSequence csq) {
      result.append(csq);
      return this;
    }

    @Override
    public Appendable append(char c) {
      result.append(c);
      return this;
    }

    @Override
    public Appendable append(CharSequence csq, int start, int end) {
      result.append(csq, start, end);
      return this;
    }