static simplyCached CharComparator ciCharComparator() {
  ret new ciCharComparator_C;
}

final sclass ciCharComparator_C implements CharComparator {
  public int compare(char c1, char c2) {
    if (c1 == c2) ret 0;
    c1 = Character.toUpperCase(c1);
    c2 = Character.toUpperCase(c2);
    if (c1 == c2) ret 0;
    c1 = Character.toLowerCase(c1);
    c2 = Character.toLowerCase(c2);
    // No overflow because of numeric promotion
    ret c1 - c2;
  }
}

Began life as a copy of #1014136