Java CLI - Conversion Temperature

ConvTemp.java

import javax.swing.*;
public class KonversiTemperatur {
    public static void main(String[] args) {
        double tempC, tempR, tempF;
        String bilangan = JOptionPane.showInputDialog("Masukkan Celcius : ");
        System.out.println("Masukkan angka : " + bilangan);
        tempC = Double.parseDouble(bilangan);
        tempR = tempC*4/5;
        tempF = tempC*9/5+32.0;
        System.out.println("Temperature Celcius = " + tempC );
        System.out.println("Temperature Reamur = " + tempR );
        System.out.println("Temperature Fahrenheit = " + tempF );
        System.exit(0);
    }
}