Nomor 1 If Else

package tugasif1;
import java.io.*;
/**
 *
 * @author kalvin jr
 */
public class Tugasif1 {
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
    DataInputStream a = new DataInputStream(System.in);
    String nama,stb,almt,grade,ket;
    int nm,nf,nt;
    double na;
    try{
        System.out.print("Masukkan Stambuk : ");
        stb = a.readLine();
        System.out.print("Masukkan Nama : ");
        nama=a.readLine();
        System.out.print("Masukkan Alamat : ");
        almt =a.readLine();
        System.out.print("Masukkan Nilai Tugas : ");
        nt =Integer.parseInt(a.readLine());
        System.out.print("Masukkan Nilai MID : ");
        nm = Integer.parseInt(a.readLine());
        System.out.print("Masukkan Nilai Final :");
        nf=Integer.parseInt(a.readLine());

        na = ((0.3*nt)+(0.3*nm)+(0.4*nf));

        if(na >= 80 && na <=100)
        { grade = "A"; ket="Sangat Baik"; }
        else if (na >= 65 && na < 80)
        { grade = "B"; ket="Baik";}
        else if (na >= 50 && na <65)
                { grade ="C"; ket="Kurang"; }
        else if (na >= 35 && na <50 ){
            grade ="D"; ket ="Sangat Kurang";}
        else
        {
            grade="E"; ket ="Eror";
        }
        System.out.println("\n\n");
        System.out.println("==========Menghitung Nilai Mahasiswa============");
        System.out.println("\n");
        System.out.println("STAMBUK\t\t: "+stb);
        System.out.println("NAMA\t\t: "+nama);
        System.out.println("ALAMAT\t\t: "+almt);
        System.out.println("NILAI TUGAS\t: "+nt);
        System.out.println("NILAI MID\t: "+nm);
        System.out.println("NILAI Final\t: "+nf);
        System.out.println("NILAI AKHIR\t: "+na);
        System.out.println("NILAI HURUF\t: "+grade);
        System.out.println("KETERANGAN\t: "+ket);
    }catch(IOException io){
        System.out.print("Eror :"+io.getMessage());}
    }
        // TODO code application logic here
 }