It's won't work WHY!!!

Question

It compiles but I can't convert Strings to Integers
Heres the code the classes involved work as I've tested them.
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
import StudentMarks;
class StudentGrades extends JFrame implements ActionListener
     private JTextField field1;
     private JTextField field2;
     private JTextField field3;
     private JTextField field4;
     private JLabel word1;
     private JLabel word2;
     private JLabel word3;
     private JLabel word4;
     private JPanel main;
     private JPanel panel;
     private JPanel button;
     private JPanel output;
     private JButton EnterStudent;
     private JButton DisplayGrade;
     private JButton ClearFields;
     private JButton Quit;
     private JTextField displayField;
     private StudentMarks sml;
     public StudentGrades()
          setTitle("Student Grades");     //Title
          setSize (500,600);     //Size
          addWindowListener (new WindowAdapter()
          { public void windowClosing(WindowEvent e)
               {System.exit(0);  //halt the program
               //Word and Fields
               word1= new JLabel ("Enter Student ID");
               word1.setHorizontalAlignment(JLabel.RIGHT);
               field1=new JTextField(" ");
               field1.addActionListener(this);
               word2 = new JLabel ("Enter Student Name");
               word2.setHorizontalAlignment(JLabel.RIGHT);
               field2= new JTextField(" ");
               field2.addActionListener(this);
               word3 = new JLabel ("Enter Mark 1");
               word3.setHorizontalAlignment(JLabel.RIGHT);
               field3 = new JTextField (" ");
               field3.addActionListener(this);
               word4= new JLabel ("Enter Mark 2");
               word4.setHorizontalAlignment(JLabel.RIGHT);
               field4 = new JTextField(" ");
               field4.addActionListener(this);
               //Add to panel the words and fields
               panel= new JPanel(new GridLayout (4,2,5,5));
               panel.add(word1);
               panel.add(field1);
               panel.add(word2);
               panel.add(field2);
               panel.add(word3);
               panel.add(field3);
               panel.add(word4);
               panel.add(field4);
               button = new JPanel();
               button.setBackground(Color.white);
               EnterStudent = new JButton("Enter Student");
               DisplayGrade = new JButton("DisplayGrade");
               ClearFields = new JButton("Clear Fields");
               Quit = new JButton("Quit");
               button.add(EnterStudent);
               button.add(DisplayGrade);
               button.add(ClearFields);
               button.add(Quit);
               EnterStudent.addActionListener(this);
               DisplayGrade.addActionListener(this);
               ClearFields.addActionListener(this);
               Quit.addActionListener(this);
               //The display field
               displayField = new JTextField(" ");
               displayField.setEditable(false);
               displayField.setHorizontalAlignment(JTextField.CENTER);
               output = new JPanel();
               output.add(displayField,BorderLayout.SOUTH);
          //addWindowListener();
          //infield.addActionListener(this)     
          main = new JPanel(new GridLayout(6,4,5,5));
          main.add(panel,BorderLayout.NORTH);
          main.add(button,BorderLayout.CENTER);
          main.add(displayField,BorderLayout.SOUTH);
          Container contentPane = getContentPane();
          contentPane.add(main);
          public void actionPerformed (ActionEvent evt)
          Object source = evt.getSource();
                    if(source == Quit) System.exit(0);
                    else if (source == EnterStudent)
                              //StudentMarks butt1;
                              //String x = field1.getText();
                              //String name = field2.getText();
                              //String mak1 = field3.getText();
                              //String mak2 = field4.getText();
                              //Integer id = new Integer(field1.getText());
                              //Integer mark1 = new Integer(field3.getText());
                              //Integer mark2 = new Integer(field4.getText());
                              //sml = new StudentMarks(1,"Baza",25,45);
                              sml = new StudentMarks(Integer.parseInt(field1.getText()),field2.getText(),Integer.parseInt(field3.getText()),Integer.parseInt(field4.getText()));
                              displayField.setText("Student " + sml.getID() + " marks have been entered");
                         else if (source == DisplayGrade)
                         //{sml = new StudentMarks(Integer.parseInt(field1.getText()),field2.getText(),Integer.parseInt(field3.getText()),Integer.parseInt(field4.getText()));
                         displayField.setText(sml + "\n" + sml.getGrade());
                         //StudentMarks butt2;
                         //String x = field1.getText();
                         //String name = field2.getText();
                         //String mak1 = field3.getText();
                         //String mak2 = field4.getText();
                         //int id, mark1, mark2;
                         //id = Integer.parseInt(x);
                         //mark1 = Integer.parseInt(mak1);
                         //mark2 = Integer.parseInt(mak2);
                         //butt2 = new StudentMarks(id,name,mark1,mark2);
                         //displayField.setText(butt2.getGrade());
else if (source == ClearFields)
                              field1.setText(" ");
                              field2.setText(" ");
                              field3.setText(" ");
                              field4.setText(" ");
                              displayField.setText(" ");
     public class StudentGradesTest
     {     public static void main (String[] args)
          {     StudentGrades s = new StudentGrades();
               s.show();
     }

Answer 1

Try getText().trim()
This will remove spaces from the text & avoid NumberFormatException being thrown
Warm regards
Aswin Asokan