public String getUserId() {
        return username;
    }

    /**
     * Returns a string representation of this credential.
     *
     * @return A string representation containing the username in braces
     */
    @Override
    public String toString() {
        return "{" + username + "}";
    }

      builder.append(args[i++]);
      templateStart = placeholderStart + 2;
    }
    builder.append(template.substring(templateStart));

    // if we run out of placeholders, append the extra args in square braces
    if (i < args.length) {
      builder.append(" [");
      builder.append(args[i++]);
      while (i < args.length) {
        builder.append(", ");
        builder.append(args[i++]);
      }

   *     argument. These are matched by position - the first {@code %s} gets {@code
   *     errorMessageArgs[0]}, etc. Unmatched arguments will be appended to the formatted message in
   *     square braces. Unmatched placeholders will be left as-is.
   * @param errorMessageArgs the arguments to be substituted into the message template. Arguments
   *     are converted to strings using {@link String#valueOf(Object)}.

 */
internal fun String.toCanonicalHost(): String? {
  val host: String = this

  // If the input contains a :, it’s an IPv6 address.
  if (":" in host) {
    // If the input is encased in square braces "[...]", drop 'em.
    val inetAddressByteArray =
      (
        if (host.startsWith("[") && host.endsWith("]")) {
          decodeIpv6(host, 1, host.length - 1)
        } else {

        '^'.code,
        '`'.code,
        '{'.code,
        '|'.code,
        '}'.code,
      ).test(UrlComponentEncodingTester.Component.HOST)
  }

  @Test
  fun hostIpv6() {
    // Square braces are absent from host()...
    assertThat(parse("http://[::1]/").host).isEqualTo("::1")

    // ... but they're included in toString().
    assertThat(parse("http://[::1]/").toString()).isEqualTo("http://[::1]/")

   *
   *  * A regular host name, like `android.com`.
   *
   *  * An IPv4 address, like `127.0.0.1`.
   *
   *  * An IPv6 address, like `::1`. Note that there are no square braces.
   *
   *  * An encoded IDN, like `xn--n3h.net`.
   *
   * | URL                   | `host()`        |
   * | :-------------------- | :-------------- |
   * | `http://android.com/` | `"android.com"` |

      To apply the Apache License to your work, attach the following
      boilerplate notice, with the fields enclosed by brackets "[]"
      replaced with your own identifying information. (Don't include
      the brackets!)  The text should be enclosed in the appropriate
      comment syntax for the file format. We also recommend that a

    opcode = b0 and B0_MASK_OPCODE
    isFinalFrame = b0 and B0_FLAG_FIN != 0
    isControlFrame = b0 and OPCODE_FLAG_CONTROL != 0

    // Control frames must be final frames (cannot contain continuations).
    if (isControlFrame && !isFinalFrame) {
      throw ProtocolException("Control frames must be final.")
    }

    val reservedFlag1 = b0 and B0_FLAG_RSV1 != 0
    when (opcode) {
      OPCODE_TEXT, OPCODE_BINARY -> {

    UnicodeEscaper spaceEscaper = new PercentEscaper(" ", false);

    assertEquals("string%20with%20spaces", basicEscaper.escape("string with spaces"));
    assertEquals("string+with+spaces", plusForSpaceEscaper.escape("string with spaces"));
    assertEquals("string with spaces", spaceEscaper.escape("string with spaces"));
  }

  /** Tests that if we add extra 'safe' characters they remain unescaped */
  public void testCustomEscaper() {

 *  * [onHeaders] (unless canceled)
 *  * [onData] (optional sequence of data frames)
 *
 * As a stream ID is scoped to a single HTTP/2 connection, implementations which target multiple
 * connections should expect repetition of stream IDs.
 *
 * Return true to request cancellation of a pushed stream.  Note that this does not guarantee
 * future frames won't arrive on the stream ID.
 */
interface PushObserver {
  /**