Java How To Program, Late Objects, 11th Edition

... get part number
29      public String getPartNumber() {return partNumber;}
30
31      // get description
32      public String getPartDescription() {return partDescription;}
33
34      // get quantity
35      public int getQuantity() {return quantity;}
36
37      // get price per item
38      public double getPricePerItem() {return pricePerItem;}
39
40      // return String representation of Invoice object
41      @Override
42      public String toString() {
43         return String.format("%s: %n%s: %s (%s) %n%s: %d %n%s: $%,.2f",
44            "invoice", "part number", getPartNumber(), getPartDescription(),
45            "quantity", getQuantity(), "price per item", getPricePerItem());
46      }  
47
48      // method required to carry out contract with interface Payable     
49      @Override                                                           
50      public double getPaymentAmount() {                                  
51         return