Java: JOptionPane Input

Question

I've got a code for a program which is converting (SI) units to an other one. I am working with JOptionPane, and it is working. But I have the problem that I have to input the numbers 8 times and not just 2 times.

Can anyone suggest a solution?

import javax.swing.JOptionPane;

class Aufgabe {

    // Newton in Kilopond
    static double newton(){
        double e = readin()[0];
        double newton = e*0.10197;
        return newton;
    }

    // Kilopond in Newton
    static double kilopond(){
        double f = readin()[1];
        double kilopond = f/0.10197;
        return kilopond;
    }

    // method readin
    static double[] readin(){
        String a = JOptionPane.showInputDialog("newton:");
        String b = JOptionPane.showInputDialog("kilopond:");
        double n = Double.parseDouble(a);
        double k = Double.parseDouble(b);
        return new double[]{n, k};
    }

    // Main-Methode
    public static void main (String[] args) {
        double a = readin()[0];
        double b = readin()[1];
        double c = newton();
        double d = kilopond();
        System.out.println(a + " N = " + c + "kp"); 
        System.out.println(b + " kp = " + d + "N");
    }
}

Answer 1

Every time you write readin(), the method is called, and the user is requested to type the two values. This happens in four places in your code, for a total of 8 dialog boxes.

Instead, call the method just once. Store the return value in a variable and pass the necessary value as an argument to methods that need it:

class Aufgabe {

    private static final double CONVERSION_FACTOR = 0.10197;

    // Newton in Kilopond
    static double newton(double e) {
        double newton = e * CONVERSION_FACTOR;
        return newton;
    }

    // Kilopond in Newton
    static double kilopond(double f) {
        double kilopond = f / CONVERSION_FACTOR;
        return kilopond;
    }

    // method readin
    static double[] readin() {
        String a = JOptionPane.showInputDialog("newton:");
        String b = JOptionPane.showInputDialog("kilopond:");
        double n = Double.parseDouble(a);
        double k = Double.parseDouble(b);
        return new double[] { n, k };
    }

    // Main-Methode
    public static void main(String[] args) {
        double[] valuesRead = readin();
        double a = valuesRead[0];
        double b = valuesRead[1];
        double c = newton(a);
        double d = kilopond(b);
        System.out.println(a + " N = " + c + "kp");
        System.out.println(b + " kp = " + d + "N");
    }
}