Question

Invoice Class - Create a class called Invoice that a hardware store might use to represent an invoice for an item sold at the store. An Invoice should include four pieces of information as instance variables—a part number (type String), a part description (type String), a quantity of the item being purchased (type int) and a price per item (double).

• Your class should have a constructor that initializes the four instance variables. If the quantity passed to the constructor is not positive, it should be set to 0 by the constructor. If the price per item passed to the constructor is not positive, it should be set to 0.0 by the constructor.

• Provide a set and a get method for each instance variable. If the quantity passed to the setQuantity method is not positive, it should be set to 0 by the method. If the price per item passed to the setPricePerItem method is not positive, it should be set to 0.0 by the method.

• Provide a method named getInvoiceAmount that calculates the invoice amount (i.e., multiplies the quantity by the price per item), then returns the amount as a double value.

Write a test app named InvoiceTest that demonstrates class Invoice’s capabilities. Create two Invoice objects, print their state, and invoice amounts.

(Java Programming)

Answer 1

Java Program:

package invoicedriver;

class Invoice {
   //Private data members
   private String partNumber;
   private String partDescription;
   private int quantity;
   private double pricePerItem;

//Constructor
public Invoice(String partNumber, String partDescription, int quantity, double pricePerItem) {
this.partNumber = partNumber;
this.partDescription = partDescription;
//Checking values
if(quantity < 0) {
this.quantity = 0;
}
else {
this.quantity = quantity;
}
if(pricePerItem < 0) {
this.pricePerItem = 0.0;
}
else {
this.pricePerItem = pricePerItem;
}
}
  
//Setter and Getter methods
public String getPartNumber() {
return partNumber;
}

public void setPartNumber(String partNumber) {
this.partNumber = partNumber;
}

public String getPartDescription() {
return partDescription;
}

public void setPartDescription(String partDescription) {
this.partDescription = partDescription;
}

public int getQuantity() {
return quantity;
}

public void setQuantity(int quantity) {
//Checking values
if(quantity < 0) {
this.quantity = 0;
}
else {
this.quantity = quantity;
}
}

public double getPricePerItem() {
return pricePerItem;
}

public void setPricePerItem(double pricePerItem) {
//Checking values
if(pricePerItem < 0) {
this.pricePerItem = 0.0;
}
else {
this.pricePerItem = pricePerItem;
}
}
  
//Method that calculates the invoice amount
public double getInvoiceAmount() {
return (this.quantity * this.pricePerItem);
}
}

public class InvoiceDriver {

//Main method
public static void main(String[] args) {
  
//Creating objects
Invoice inv1 = new Invoice("P101", "Android Mobiles", 10, 23.5);
Invoice inv2 = new Invoice("P201", "Tablet", 5, 14.9);
  
//Printing result
System.out.println("\nInvoice 1: \n\n Part Number: " + inv1.getPartNumber() + "\n Description: " + inv1.getPartDescription() + "\n Invoice Amount: $" + inv1.getInvoiceAmount());
System.out.println("\nInvoice 2: \n\n Part Number: " + inv2.getPartNumber() + "\n Description: " + inv2.getPartDescription() + "\n Invoice Amount: $" + inv2.getInvoiceAmount());
}
}
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Sample Run: