(JAVA)

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 purchased (type int), and a price per item (double). Your class should have a constructor that initializes the four instance variables. Provide an accessorand mutator method for each instance variable. In addition, provide a method called getInvoiceAmount() that calculates the invoice amount (e.g. multiplies the quantity times the price per item, then returns the amount as a double value), a toString() method that returns the state of the Invoice object, and an equals() method that compares two Invoice objects. Please make sure that if the quantity is not positive, it should be set to zero. If the price per item is not positive, it should be set to 0.0. Write a client test application named InvoiceTest that demonstrates class Invoices capabilities (e.g. test ALL methods of the Invoice class).