code: public static <T extends Appendable> T appendNumber(T result, int n,
              int radix, int minDigits)
      {
          try {
              if (radix < 2 || radix > 36) {
                  throw new IllegalArgumentException("Illegal radix " + radix);
              }
  
  
              int abs = n;
  
              if (n < 0) {
                  abs = -n;
                  result.append("-");
              }
  
              recursiveAppendNumber(result, abs, radix, minDigits);
  
              return result;
          } catch (IOException e) {
              throw new IllegalIcuArgumentException(e);
          }
  
      }
docs: Append a number to the given Appendable in the given radix.
  Standard digits '0'-'9' are used and letters 'A'-'Z' for
  radices 11 through 36.
  @param result the digits of the number are appended here
  @param n the number to be converted to digits; may be negative.
  If negative, a '-' is prepended to the digits.
  @param radix a radix from 2 to 36 inclusive.
  @param minDigits the minimum number of digits, not including
  any '-', to produce.  Values less than 2 have no effect.  One
  digit is always emitted regardless of this parameter.
  @return a reference to result