我需要将双“amt”格式化为美元金额 println("$"+ dollar + "."+ cents)，以便小数点后有两位数。

这样做的最佳方法是什么？

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) + ".");
}

最佳答案

使用 NumberFormat.getCurrencyInstance() :

double amt = 123.456;    

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

输出:

$123.46

https://stackoverflow.com/questions/13791409/