Payable interface declaration 1 2 3 4 public interface Payable 5 { 6 double getP

Question

Payable interface declaration
1
2
3
4 public interface Payable
5 {
6 double getPaymentAmount();

7 }


Invoice class that implements Payable
1
3
4 public class Invoice implements Payable
5 {
6 private String partNumber;
7 private String partDescription;
8 private int quantity;
9 private double pricePerItem;
10
11
12 public Invoice( String part, String description, int count,
13 double price )
14 {
15 partNumber = part;
16 partDescription = description;
17 setQuantity( count );
18 setPricePerItem( price );
19 }
20
21
22 public void setPartNumber( String part )
23 {
24 partNumber = part;
25 }
26
27
28 public String getPartNumber()
29 {
30 return partNumber;
31 }
32
33
34 public void setPartDescription( String description )
35 {
36 partDescription = description;
37 }
38
39
40 public String getPartDescription()
41 {
42 return partDescription;
43 }
44
45
46 public void setQuantity( int count )
47 {
48 quantity = ( count < 0 ) ? 0 : count; // quantity cannot be negative
49 }
50
51
52 public int getQuantity()
53 {
54 return quantity;
55 }
56
58 public void setPricePerItem( double price )
59 {
60 pricePerItem = ( price < 0.0 ) ? 0.0 : price; // validate price
61 }
62
63
64 public double getPricePerItem()
65 {
66 return pricePerItem;
67 }
68
69
70 public String toString()
71 {
72 return String.format( "%s: %s: %s (%s) %s: %d %s: $%,.2f",
73 "invoice", "part number", getPartNumber(), getPartDescription(),
74 "quantity", getQuantity(), "price per item", getPricePerItem() );
75 }
76
77 // method required to carry out contract with interface Payable
78 public double getPaymentAmount()
79 {
80 return getQuantity() * getPricePerItem(); // calculate total cost
81 }
82 }

Payable interface test program processing Invoices and Employees polymorphically.

3
4 public class PayableInterfaceTest
5 {
6 public static void main( String args[] )
7 {
8
9 Payable payableObjects[] = new Payable[ 4 ];
10
11
12 payableObjects[ 0 ] = new Invoice( "01234", "seat", 2, 375.00 );
13 payableObjects[ 1 ] = new Invoice( "56789", "tire", 4, 79.95 );
14 payableObjects[ 2 ] =
15 new SalariedEmployee( "John", "Smith", "111-11-1111", 800.00 );
16 payableObjects[ 3 ] =
17 new SalariedEmployee( "Lisa", "Barnes", "888-88-8888", 1200.00 );
18
19 System.out.println(
20 "Invoices and Employees processed polymorphically: " );
21
22
23 for ( Payable currentPayable : payableObjects )
24 {
25 amount
26 System.out.printf( "%s %s: $%,.2f ",
27 currentPayable.toString(),
28 "payment due", currentPayable.getPaymentAmount() );
29 }
30 }
31 }

Use the program shown in Table 1, then change the interface Payable to an Abstract class.

Insert the description of each class, plus the class diagram of your program here.

Explanation / Answer

Payable interface declaration 1 2 3 4 public interface Payable 5 { 6 double getPaymentAmount(); 7 } Invoice class that implements Payable 1 3 4 public class Invoice implements Payable 5 { 6 private String partNumber; 7 private String partDescription; 8 private int quantity; 9 private double pricePerItem; 10 11 12 public Invoice( String part, String description, int count, 13 double price ) 14 { 15 partNumber = part; 16 partDescription = description; 17 setQuantity( count ); 18 setPricePerItem( price ); 19 } 20

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