toString method
Returns a string representation of this number, in either standard or scientific notation.
If the magnitude of the number is in the range 10<sup>-3</sup>, 10<sup>8</sup>
standard notation will be used. Otherwise, scientific notation will be used.
@return a string representation of this number
Implementation
String toString() {
int mag = magnitude(hi);
if (mag >= -3 && mag <= 20) return toStandardNotation();
return toSciNotation();
}