Returns a copy of this duration with the specified duration _in hours added.
!(p)
This instance is immutable and unaffected by this method call.
@param hoursToAdd the hours to add, positive or negative
@return a {@code Duration} based on this duration with the specified hours added, not null
@throws ArithmeticException if numeric overflow occurs
Returns a copy of this duration with the specified duration _in hours added. !(p) This instance is immutable and unaffected by this method call.
@param hoursToAdd the hours to add, positive or negative @return a {@code Duration} based on this duration with the specified hours added, not null @throws ArithmeticException if numeric overflow occurs