JOption Menginputkan Nilai

Jenis Program : Java Language
Specifik           : JOptionPane

package JOptPane;
import javax.swing.JOptionPane;

/**
 *
 * @author BEJI SOKHI
 */
public class Nilai {
    public static void main(String[] args) {
        int quiz;
       int tugas;
       int uts;
       int uas;
       double sum;
       String nilaiHuruf = null;

       String str1 = JOptionPane.showInputDialog("Input Quiz Value");
       quiz = Integer.parseInt(str1);
       String str2 = JOptionPane.showInputDialog("Input Assignment Value");
       tugas = Integer.parseInt(str2);
       String str3 = JOptionPane.showInputDialog("Input Mid-Test Value");
       uts = Integer.parseInt(str3);
       String str4 = JOptionPane.showInputDialog("Input Final-Test Value");
       uas = Integer.parseInt(str4);

       sum = (quiz*0.15)+(tugas*0.15)+(uts*0.3)+(uas*0.4);

        if (sum<=100 && sum>=85){
            nilaiHuruf="A";
        } else if (sum<=84 && sum>=70){
            nilaiHuruf="B";
        }else if (sum<=69 && sum>=55){
            nilaiHuruf="C";
        }else if (sum<=54 && sum>=40){
            nilaiHuruf="D";
        }else if (sum>=0 && sum<=39) {
            nilaiHuruf="E";} else {
           nilaiHuruf="Invalid Value";
            }

        System.out.println("Quiz Value            : "+quiz);
        System.out.println("Assignment Value      : "+tugas);
        System.out.println("Mid-Test Value        : "+uts);
        System.out.println("Final-Test Value      : "+uas);
        System.out.println("Your Total Scores is  : "+sum);
        System.out.println("Grade                 : "+nilaiHuruf);

        System.exit(0);
    }

}

NB: Jangan CoPas langsung ya bray