限制返回的小数位数？

Question

I'm new and trying to stick to basic concepts here. How do I limit the decimals in an answer pulled from a return in a different class?I'm not sure how to write a.calculateTuition in a price format 000.00. I couldn't find a good way to use the DecimalFormat class and Math.round() is not accurate enough for prices. Thanks in advance!

From the class:

public double creditHours;
public double calculateTuition(){
    double totalCost=0;
    double costPerHour=124.04;
    totalCost = creditHours * costPerHour;

    return totalCost;
}

From Main:

Student a=new Student();
a.setHours(3);
System.out.println("Cost is " +  a.calculateTuition());

Answer 1

Usually it's considered to be best practise to use BigDecimal with currency / money related computations because of the precision it offers.

If you decide to use BigDecimal, it also has .setScale() and many other useful methods you might find useful.

Answer 2

You can use the following utility to round the number of decimals you want, public static double round(double value, int places) { if (places < 0) throw new IllegalArgumentException();

long factor = (long) Math.pow(10, places);
value = value * factor;
long tmp = Math.round(value);
return (double) tmp / factor;
}