* @return CharSequence
         */
        public static CharSequence bbb() {
            return createCharSequence("bbb");
        }

        /**
         * @return CharSequence
         */
        public static CharSequence ccc() {
            return createCharSequence("ccc");
        }

        /**
         * @return CharSequence
         */
        public static CharSequence hoge() {

   * the same sequence when read using each type of read method it provides.
   */
  private static void assertReadsCorrectly(CharSequence charSequence) throws IOException {
    String expected = charSequence.toString();

    // read char by char
    CharSequenceReader reader = new CharSequenceReader(charSequence);

        assertArgumentNotEmpty("pattern", pattern);

        return converter(new NumberConverter(pattern), propertyNames);
    }

    /**
     * Converts an array of {@literal CharSequence} to a {@literal List} of {@literal String}.
     *
     * @param array
     *            An array of {@literal CharSequence}

   * the same sequence when read using each type of read method it provides.
   */
  private static void assertReadsCorrectly(CharSequence charSequence) throws IOException {
    String expected = charSequence.toString();

    // read char by char
    CharSequenceReader reader = new CharSequenceReader(charSequence);

      checkNotNull(sequence);
      return "";
    }

    @Override
    public String replaceFrom(CharSequence sequence, char replacement) {
      char[] array = new char[sequence.length()];
      Arrays.fill(array, replacement);
      return new String(array);
    }

    @Override
    public String replaceFrom(CharSequence sequence, CharSequence replacement) {

    }

    @Override
    public void debug(CharSequence content) {
        logger.debug(toString(content));
    }

    private String toString(CharSequence content) {
        if (content == null) {
            return "";
        } else {
            return content.toString();
        }
    }

    @Override
    public void debug(CharSequence content, Throwable error) {

    @DisplayName("Should handle StringBuilder as CharSequence")
    void testJoinWithStringBuilder() {
        StringBuilder sb1 = new StringBuilder("first");
        StringBuilder sb2 = new StringBuilder("second");
        String result = StringUtil.join(",", sb1, sb2);
        assertEquals("first,second", result);
    }

    @Test
    @DisplayName("Should handle StringBuffer as CharSequence")
    void testJoinWithStringBuffer() {

    checkNotClosed();
    target.append(c);
    return this;
  }

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

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

    public DefaultLog(Logger logger) {
        this.logger = requireNonNull(logger);
    }

    @Override
    public void debug(CharSequence content) {
        if (isDebugEnabled()) {
            logger.debug(toString(content));
        }
    }

    @Override
    public void debug(CharSequence content, Throwable error) {
        if (isDebugEnabled()) {
            logger.debug(toString(content), error);
        }
    }

   * the {@code charSequence} is mutated while it is being read, so don't do that.
   *
   * @since 15.0 (since 14.0 as {@code CharStreams.asCharSource(String)})
   */
  public static CharSource wrap(CharSequence charSequence) {
    return charSequence instanceof String
        ? new StringCharSource((String) charSequence)
        : new CharSequenceCharSource(charSequence);
  }

  /**