java how to program exercise 3.13

java how to program exercise 3.13
Source Code:
public class InvoiceTest {


/**
* @param args the command line arguments
*/
public static void main(String[] args) {
Invoice obj = new Invoice("0123","this is a example",20,35.26);
System.out.printf("the invoice amount is = %.2f",obj.getInvoiceAmount());



}

}
class Invoice
{
private String partNumber;
private String partDescription;
private int purchasedItemQuantity;
private double itemPrice;

public Invoice(String pName, String pDescription, int piQuantity, double iPrice )
{
partNumber = pName;
partDescription = pDescription;
purchasedItemQuantity = piQuantity;
itemPrice = iPrice;

}


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 getPurchasedItemQuantity() {
return purchasedItemQuantity;
}


public void setPurchasedItemQuantity(int purchasedItemQuantity) {
this.purchasedItemQuantity = purchasedItemQuantity;
}


public double getItemPrice() {
return itemPrice;
}


public void setItemPrice(double itemPrice) {
this.itemPrice = itemPrice;
}


public double getInvoiceAmount()
{
if(getPurchasedItemQuantity() (use less than sign here)0)
{
setPurchasedItemQuantity(0);
}
else if(getItemPrice()(use less than sign here)0.0)
setItemPrice(0.0);

double invoiceamount = getPurchasedItemQuantity()*getItemPrice();
return invoiceamount;
}



}