public static Days ofWeeks(int weeks) {
        if (weeks == 0) {
            return ZERO;
        }
        return new Days(Math.multiplyExact(weeks, DAYS_PER_WEEK));
    }
public static Days ofWeeks ( int weeks ) { if ( weeks == 0 ) { return ZERO ; } return new Days ( Math . multiplyExact ( weeks , DAYS_PER_WEEK ) ) ; }
Obtains a {@code Days} representing the number of days
equivalent to a number of weeks.
<p>
The resulting amount will be day-based, with the number of days
equal to the number of weeks multiplied by 7.

@param weeks  the number of weeks, positive or negative
@return the amount with the input weeks converted to days, not null
@throws ArithmeticException if numeric overflow occurs