Question

3.12 (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. Provide a set and a get method for each instance variable. In addition, 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. If the quantity is not positive, it should be set to 0. If the price per item is not positive, it should be set to 0.0. Add a main method to the class that demonstrates class Invoice's capabilities by reading in values from stdin and prints to stdout the complete state of the object each time the state of the object is changed.

This is for an intro to java

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: