How to get alphabet from result if-else

I have trouble with this, I want the alphabet from if-else function is showing in text area with "Grade : ", but as you can see, the result is like that.

I want when i click the button the text "Grade : " in the textarea must like "Grade : D", what I miss?

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    String nim1,nama1,textsemester;
    String nilaik = nilai_kehadiran.getText();
    int tnilaik=Integer.parseInt(nilaik);
    int totalnilaik=tnilaik*10/100;
    String nilait=nilai_tugas.getText();
    int tnilait=Integer.parseInt(nilait);
    int totalnilait=tnilait*20/100;
    String nilaiu=nilai_uts.getText();
    int tnilaiu=Integer.parseInt(nilaiu);
    int totalnilaiu=tnilaiu*30/100;
    String nilaiua=nilai_uas.getText();
    int tnilaiua=Integer.parseInt(nilaiua);
    int totalnilaiua=tnilaiua*40/100;
    
    int nilaipemrograman=totalnilaik+totalnilait+totalnilaiu+totalnilaiua;
    
    nim1=nim.getText();
    nama1=nama.getText();
    textsemester=semester.getText();
    
   
    String gender = String.valueOf(buttonGroup1.getSelection().getActionCommand());
    
    textarea.append("NIM \t: " + nim1 + "\n" );
    textarea.append("NAMA \t: " + nama1 + "\n");
    textarea.append("Jenis Kelamin \t: " + gender + "\n");
    textarea.append("Semester \t: " + textsemester + "\n");
    textarea.append("Nilai Kehadiran \t: " + totalnilaik + "\n");
    textarea.append("Nilai Tugas \t: " + totalnilait + "\n");
    textarea.append("Nilai UTS \t: " + totalnilaiu + "\n");
    textarea.append("Nilai UAS \t: " + totalnilaiua + "\n");
    textarea.append("Nilai Pemrograman II \t: " + nilaipemrograman +"\n");
    textarea.append("Grade \t: " + grade);
    
    nilai_pemrograman.setText(Integer.toString(nilaipemrograman));
    
    if(nilaipemrograman < 50)
    grade.setText("E");
    else if(nilaipemrograman >= 50)
        grade.setText("D");
    else if(nilaipemrograman >= 60)
        grade.setText("C");
    else if(nilaipemrograman >= 70)
        grade.setText("B");
    else if(nilaipemrograman >= 80)
        grade.setText("A");

please help me