formatting - Java - format double value as dollar amount

Question

I need to format the double "amt" as a dollar amount println("$" + dollars + "." + cents) such that there are two digits after the decimal.

What is the best way to go about doing so?

if (payOrCharge <= 1)
{
    System.out.println("Please enter the payment amount:");
    double amt = keyboard.nextDouble();
    cOne.makePayment(amt);
    System.out.println("-------------------------------");
    System.out.println("The original balance is " + cardBalance + ".");
    System.out.println("You made a payment in the amount of " + amt + ".");
    System.out.println("The new balance is " + (cardBalance - amt) + ".");
}
else if (payOrCharge >= 2)
{
    System.out.println("Please enter the charged amount:");
    double amt = keyboard.nextDouble();
    cOne.addCharge(amt);
    System.out.println("-------------------------------");
    System.out.println("The original balance is $" + cardBalance + ".");
    System.out.println("You added a charge in the amount of " + amt + ".");
    System.out.println("The new balance is " + (cardBalance + amt) + ".");
}

Answer 1

Use NumberFormat.getCurrencyInstance():

double amt = 123.456;    

NumberFormat formatter = NumberFormat.getCurrencyInstance();
System.out.println(formatter.format(amt));

Output:

$123.46