Uso de CheckBox, ComboBox y Radio Button en Java NetBeans 

Si donde esta ese condigo me podrías decir por favor

The append() method is available in the StringBuilder class, but not in the JTextArea class. To concatenate strings in JTextArea, you can use the setText() method. Here is a modified version of your Semestre() method that uses setText() to concatenate the semester number to the text area: java public void Semestre(){ // Check which radio button is selected if(Radio1.isSelected()){ // Set the text of the text area to "Semestre: N°1" TxtArea1.setText(" Semestre: " + "N°1"); } else if(Radio2.isSelected()){ // Set the text of the text area to "Semestre: N°2" TxtArea1.setText(" Semestre: " + "N°2"); } else if(Radio3.isSelected()){ // Set the text of the text area to "Semestre: N°3" TxtArea1.setText(" Semestre: " + "N°3"); } else if(Radio4.isSelected()){ // Set the text of the text area to "Semestre: N°4" TxtArea1.setText(" Semestre: " + "N°4"); } else if(Radio5.isSelected()){ // Set the text of the text area to "Semestre: N°5" TxtArea1.setText(" Semestre: " + "N°5"); } else if(Radio6.isSelected()){ // Set the text of the text area to "Semestre: N°6" TxtArea1.setText(" Semestre: " + "N°6"); } } This modified method should work as expected.