Calculating totalCost - subtotal

Question

Ok below is my code for a class I am taking... I need to know how to properly code the totalCost for this product and I can not for the life of me figure out how to properly do this. The price per product is $1 and I need to calculate a 7% sales tax as well. Help!!!
import javax.swing.JOptionPane;
/**
* #author bary
*/
public class CocaCola1 {
public static void main(String[] args)
{
String openingMsg = "*** Welcome to CocaCola Online Ordering System ***\n"
+ "Do yourself a favor and order some Cola... NOW!";
JOptionPane.showMessageDialog(null, openingMsg);
System.out.println(0);
String name = getUserInput("What is your name?");
System.out.println(name);
String returnCustomer = getUserInput("Are you a returning customer? (yes/no)");
System.out.println(returnCustomer);
String orderType = getUserInput("Would you like to purchase Dasani, Coke, Diet Coke, or Cherry Coke?");
System.out.println(orderType);
String orderAmount = getUserInput("How many units would you like to purchase?");
System.out.println(orderAmount);
Integer.parseInt(orderAmount);
// each unit costs $1.00 so orderAmount is equal to cost per unit
double salesTax = 0.7;
// create and display output string
String outputMsg
= "Hello " + name + ".\n\n" +
"Your return customer status is " + returnCustomer + ".\n" +
"You ordered " + orderAmount +
" units of " + orderType + ".\n" +
"Your total cost is $" + orderAmount + salesTax + ".\n" +
"Thank you for visiting CocaCola" + ".\n\n" +
"Your order will be proccessed ASAP.\n";
JOptionPane.showMessageDialog(null, outputMsg);
}
private static String getUserInput(String prompt)
{
int failCount = 0;
do
{
String answer = JOptionPane.showInputDialog(prompt);
if (answer == null)
{
System.exit(0);
}
answer = answer.trim();
if (answer.isEmpty())
{
JOptionPane.showMessageDialog(null, "You must provide a non-blank answer");
failCount = failCount + 1;
} else
{
return answer;
}
} while (failCount < 3);
JOptionPane.showMessageDialog(null, "You failed three times to provide input... Try again later!");
System.exit(0);
return null; // means nothing, as I just exited on the prior line, but need it to compile
} // end main()
} // end class CocaCola1

Answer 1

orderAmount + salesTax would only be if the sales tax was static. You need to multiply the orderAmount by the sales tax and add salestax
ex: orderAmount*salesTax+prderAmount
or set salesTax to 1.7 and it would be
orderAmount*salesTax