Polymorphism and Abstract Classes - Absolute Java - page 492

Display 8.2 The Derived Class DiscountSale (part 1 of 2)

1 /**
2 Class for a sale of one item with discount expressed as a percent of
3 the price, but no other adjustments.
4 Class invariant: The price is always nonnegative; the name is a
5 nonempty string; the discount is always nonnegative.
6 */

7 public class DiscountSale extends Sale
8 {
9 private double discount; //A percent of the price. Cannot be

//negative.

10 public DiscountSale()
11 {
12 super ();
13 discount = 0;
14 }

The meaning would be unchanged if
this line were omitted.

15 /**

16 Precondition: theName is a nonempty string; thePrice is

nonnegative; theDiscount is expressed as a percent of the price

17 and is nonnegative.

18 */

19 public DiscountSale(String theName,

20 double thePrice, double theDiscount)

21 {
22 super (theName, thePrice);
23 setDiscount(theDiscount);
24 }

25 public DiscountSale(DiscountSale originalObject)
26 {
27 super (originalObject);
28 discount = originalObject.discount;
29 }

30 public static void announcement()
31 {
32 System.out.println("This is the DiscountSale class.");
33 }

34 public double bill()
35 {
36 double fraction = discount/100;

37 return (1 − fraction)*getPrice();

38 }