Follopw instructions to define Invoice class. The attributes are private but not final. Define required $4$ setters and $4$ getters.:package Invoice;

public class Invoice $\{$

private final String partNumber;

private final String partDescription;

private final int quantity;

private final double pricePerItem;

public Invoice$($String partNumber, String partDescription, int quantity, double pricePerItem$)\{$

this.partNumber $=$ partNumber;

this.partDescription $=$ partDescription;

this.quantity $=$ quantity;

this.pricePerItem $=$ pricePerItem;

$\}$

public double getInvoiceTotal$()\{$

if $($quantity $<0)\{$

return $0$;

$\}$ else $\{$

return quantity $*$ pricePerItem;

$\}$

$\}$

$//$ getters and setters for each attribute