Working Through Printf And Void

I have a program that I have created from scratch called Product and I also created a Tester program to test my theory. The only problem that I have is that I am getting an error with this statement System.out.printf statement. The statement needs to print out "Program [name = HP ENVY x360 TouchSmart, price = $xxxxxx". The error states that "The method printf(String, Object...) in the PrintStream is not applicable for the arguments (String, String, void).

Which tells me that it is referencing back to the class file where I have

public void applyDiscount(double percent) {
percent = price - (price * percent); //establishing the discount
}

The lines of code in my tester file are (partly displayed)

String formatString = "Product[name = %s, price = %.2f]
";
System.out.printf(formatString, product.getName(), product.getPrice())
//user input the discount amount
System.out.println("
Enter discount percentage [0 - 100]: %.2f ");
double discount = user_input.nextDouble();
System.out.printf(formatString, product.getName(), product.applyDiscount(discount)); //This is the line giving me an error.
}