public String toString (int radix)

Returns the String representation of this BigInteger in the given radix. If the radix is outside the range from Character.MIN_RADIX to Character.MAX_RADIX inclusive, it will default to 10 (as is the case for Integer.toString). The digit-to-character mapping provided by Character.forDigit is used, and a minus sign is prepended if appropriate. (This representation is compatible with the (String, constructor.)

Parameters:
radix    radix of the String representation.

Returns:  String representation of this BigInteger in the given radix.

See also:
Integer.toString, Character.forDigit, BigInteger(java.lang.String, int)