我如何编写这些方法？

Question

Using the following code.. I need to create two methods that take in two doubles.. dollarsNeeded returns an int number of dollars, and changeNeeded returns an int amount of change needed..

Here is the code I'm given..

---

import javax.swing.JOptionPane;

public class MoneyNeededTester
{
    public static void main(String[] args)
    {
        double a = 5.05, b = 10.25;

        String output = "";

        output = "If you purchased an item that cost $" +a+ ", and another that cost $"+b+"\n";
        output += "it would cost you " + MoneyNeeded.dollarsNeeded(a,b) +" dollars and "+MoneyNeeded.changeNeeded(a,b)+" cents.";
        output += "\naccording to your program.\n\n";
        output += "(The correct answer was 15 dollars and 30 cents)";
        JOptionPane.showMessageDialog(null, output);


        a = 5.82; b = 6.25;

        output = "If you purchased an item that cost $" +a+ ", and another that cost $"+b+"\n";
        output += "it would cost you " + MoneyNeeded.dollarsNeeded(a,b) +" dollars and "+MoneyNeeded.changeNeeded(a,b)+" cents.";
        output += "\naccording to your program.\n\n";
        output += "(The correct answer was 12 dollars and 7 cents)";
        JOptionPane.showMessageDialog(null, output);



        a = 5.75; b = 3.56;

        output = "If you purchased an item that cost $" +a+ ", and another that cost $"+b+"\n";
        output += "it would cost you " + MoneyNeeded.dollarsNeeded(a,b) +" dollars and "+MoneyNeeded.changeNeeded(a,b)+" cents.";
        output += "\naccording to your program.\n\n";
        output += "(The correct answer was 9 dollars and 32 cents- or perhaps 31 if your computer is annoying)";
        JOptionPane.showMessageDialog(null, output);

    }
}

Answer 1

You will need a class that contains static methods, looking at your access calls it's not tied to an instantiated object. Something like ths

public class MoneyNeeded {
    public static int dollarsNeeded(double a, double b) {
        // fill in your int-returns here
        return // [int value]
    }
    public static int changeNeeded(double a, double b) {
        // and here
        return // [int value]
    }
}

Rounding functions Math.floor() might help so, and/or integer casting such as with (int) 15.30 will give you the integer 15

Answer 2

Add following class to your code:

class MoneyNeeded {

    static int dollarsNeeded(double cost1, double cost2) {

        return (int) Math.floor(cost1 + cost2);
    }

    static int changeNeeded(double cost1, double cost2) {

        double total = cost1 + cost2;
        return (int) (100 * (total - Math.floor(total)));
    }
}