StringBuilder sb = new StringBuilder();
      for (int j = 0; j < charCount; j++) {
        int codePoint;
        // discard illegal surrogate "codepoints"
        do {
          codePoint = rnd.nextInt(maxCodePoint.value);
        } while (Character.isSurrogate((char) codePoint));
        sb.appendCodePoint(codePoint);
      }
      strings[i] = sb.toString();
    }
  }

  @Benchmark

        utf8Length += (0x7f - c) >>> 31; // branch free!
      } else {
        utf8Length += 2;
        // We can't use Character.isSurrogate(c) here and below because of GWT.
        if (MIN_SURROGATE <= c && c <= MAX_SURROGATE) {
          // Check that we have a well-formed surrogate pair.
          if (Character.codePointAt(sequence, i) == c) {
            throw new IllegalArgumentException(unpairedSurrogateMsg(i));
          }

        utf8Length += (0x7f - c) >>> 31; // branch free!
      } else {
        utf8Length += 2;
        // We can't use Character.isSurrogate(c) here and below because of GWT.
        if (MIN_SURROGATE <= c && c <= MAX_SURROGATE) {
          // Check that we have a well-formed surrogate pair.
          if (Character.codePointAt(sequence, i) == c) {
            throw new IllegalArgumentException(unpairedSurrogateMsg(i));
          }

    pos: Int,
    limit: Int,
  ): List<Int> {
    val result = mutableListOf<Int>()
    var i = pos
    while (i < limit) {
      val c = this[i]
      result +=
        when {
          c.isSurrogate() -> {
            val low = (if (i + 1 < limit) this[i + 1] else '\u0000')
            if (c.isLowSurrogate() || !low.isLowSurrogate()) {
              '?'.code
            } else {
              i++

    // into the range of surrogate characters, but if they do we must not test
    // any values in that range. To see why, consider the case where:
    // safeMin <= {hi,lo} <= safeMax
    // where {hi,lo} are characters forming a surrogate pair such that:
    // codePointOf(hi, lo) > safeMax
    // which would result in the surrogate pair being (wrongly) considered safe.

 * because of the possibility of splitting a surrogate pair. The only case in which it is safe to
 * escape strings and concatenate the results is if you can rule out this possibility, either by
 * splitting an existing long string into short strings adaptively around {@linkplain
 * Character#isHighSurrogate surrogate} {@linkplain Character#isLowSurrogate pairs}, or by starting

  }

  /**
   * Asserts that a Unicode escaper escapes the given hi/lo surrogate pair into the expected string.
   *
   * @param escaper the non-null escaper to test
   * @param expected the expected output string
   * @param hi the high surrogate pair character
   * @param lo the low surrogate pair character
   */
  public static void assertUnicodeEscaping(

  }

  /**
   * Asserts that a Unicode escaper escapes the given hi/lo surrogate pair into the expected string.
   *
   * @param escaper the non-null escaper to test
   * @param expected the expected output string
   * @param hi the high surrogate pair character
   * @param lo the low surrogate pair character
   */
  public static void assertUnicodeEscaping(

        };
    EscaperAsserts.assertBasic(surrogateEscaper);

    // A surrogate pair defining a code point within the safe range.
    String safeInput = "\uD800\uDC00"; // 0x10000
    assertThat(surrogateEscaper.escape(safeInput)).isEqualTo(safeInput);

    // A surrogate pair defining a code point outside the safe range (but both
    // of the surrogate characters lie within the safe range). It is important

    // Build up a range of surrogate pair characters to test
    int min = Character.MIN_SUPPLEMENTARY_CODE_POINT;
    int max = Character.MAX_CODE_POINT;
    int range = max - min;
    int s1 = min + (1 * range) / 4;
    int s2 = min + (2 * range) / 4;
    int s3 = min + (3 * range) / 4;
    char[] dst = new char[12];

    // Put surrogate pairs at odd indices so they can be split easily