return result;
  }

  /**
   * Returns a new array that prepends {@code element} to {@code array}.
   *
   * @param element the element to prepend to the front of {@code array}
   * @param array the array of elements to append
   * @return an array whose size is one larger than {@code array}, with {@code element} occupying
   *     the first position, and the elements of {@code array} occupying the remaining elements.

      return "[]";
    }
    StringBuilder builder = new StringBuilder(length() * 5); // rough estimate is fine
    builder.append('[').append(array[start]);

    for (int i = start + 1; i < end; i++) {
      builder.append(", ").append(array[i]);
    }
    builder.append(']');
    return builder.toString();
  }

  /**

      return "[]";
    }
    StringBuilder builder = new StringBuilder(length() * 5); // rough estimate is fine
    builder.append('[').append(array[start]);

    for (int i = start + 1; i < end; i++) {
      builder.append(", ").append(array[i]);
    }
    builder.append(']');
    return builder.toString();
  }

  /**

        }

        @Test
        @DisplayName("Should handle null in append")
        void testAppendWithNull() {
            // Test with mock
            doNothing().when(mockReferralData).append(null);
            assertDoesNotThrow(() -> mockReferralData.append(null));

            // Test with concrete implementation - behavior depends on implementation
            // May throw NullPointerException
            try {

      buildString {
        append("Certificate pinning failure!")
        append("\n  Peer certificate chain:")
        for (element in peerCertificates) {
          append("\n    ")
          append(pin(element))
          append(": ")
          append(element.subjectDN.name)
        }
        append("\n  Pinned certificates for ")
        append(hostname)
        append(":")
        for (pin in pins) {

   */
  @Override
  public final String toString() {
    byte[] bytes = getBytesInternal();
    StringBuilder sb = new StringBuilder(2 * bytes.length);
    for (byte b : bytes) {
      sb.append(hexDigits[(b >> 4) & 0xf]).append(hexDigits[b & 0xf]);
    }
    return sb.toString();
  }

  private static final char[] hexDigits = "0123456789abcdef".toCharArray();

      TestCharSource okSource = new TestCharSource(STRING);
      assertThrows(IOException.class, () -> okSource.copyTo(new TestCharSink(option)));
      // ensure reader was closed IF it was opened (depends on implementation whether or not it's
      // opened at all if sink.newWriter() throws).
      assertTrue(
          "stream not closed when copying to sink with option: " + option,

   */
  @Override
  public final String toString() {
    byte[] bytes = getBytesInternal();
    StringBuilder sb = new StringBuilder(2 * bytes.length);
    for (byte b : bytes) {
      sb.append(hexDigits[(b >> 4) & 0xf]).append(hexDigits[b & 0xf]);
    }
    return sb.toString();
  }

  private static final char[] hexDigits = "0123456789abcdef".toCharArray();

      TestCharSource okSource = new TestCharSource(STRING);
      assertThrows(IOException.class, () -> okSource.copyTo(new TestCharSink(option)));
      // ensure reader was closed IF it was opened (depends on implementation whether or not it's
      // opened at all if sink.newWriter() throws).
      assertTrue(
          "stream not closed when copying to sink with option: " + option,

      // The names are repetitive so re-use the same builder to avoid allocations.
      val fileBuilder = StringBuilder(key).append('.')
      val truncateTo = fileBuilder.length
      for (i in 0 until valueCount) {
        fileBuilder.append(i)
        cleanFiles += directory / fileBuilder.toString()
        fileBuilder.append(".tmp")
        dirtyFiles += directory / fileBuilder.toString()
        fileBuilder.setLength(truncateTo)