Hi, Here is my code:

import java.awt.event.*; import java.awt.event.KeyAdapter; import java.awt.event.KeyEvent; import javax.swing.*; import java.sql.*; public class example2 extends javax.swing.JFrame {

public example2() {

    tmark1=new JTextField();
    tmark1.addKeyListener(new TetAdapter());
    tmark2=new JTextField();
    tmark2.addKeyListener(new TetAdapter());
    ttotal=new JTextField();

    initComponents();
}

class TetAdapter extends KeyAdapter{
  public void keyReleased(KeyEvent k){
      int value1 = 0, value2 = 0;
      try{
          value1 = Integer.parseInt(tmark1.getText());
      }catch(NumberFormatException ne){
          value1 = 0;
      }
      try{
          value2 = Integer.parseInt(tmark2.getText());
      }catch(NumberFormatException ne){
          value2 = 0;
      }
      ttotal.setText(value1+value2+"");
  }

} @SuppressWarnings("unchecked") // private void initComponents() {

    ttotal = new javax.swing.JTextField();
    ltotal = new javax.swing.JLabel();
    tmark1 = new javax.swing.JTextField();
    lmark2 = new javax.swing.JLabel();
    tmark2 = new javax.swing.JTextField();
    lmark1 = new javax.swing.JLabel();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

    ttotal.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            ttotalActionPerformed(evt);
        }
    });

    ltotal.setText("TOTAL");

    lmark2.setText("MARK2");

    lmark1.setText("MARK1");

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 400, Short.MAX_VALUE)
        .addGroup(layout.createSequentialGroup()
            .addGap(19, 19, 19)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                .addComponent(ltotal, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addComponent(lmark2, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addComponent(lmark1, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
            .addGap(36, 36, 36)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                .addComponent(tmark1)
                .addComponent(tmark2, javax.swing.GroupLayout.DEFAULT_SIZE, 95, Short.MAX_VALUE)
                .addComponent(ttotal))
            .addGap(80, 80, 80))
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 300, Short.MAX_VALUE)
        .addGroup(layout.createSequentialGroup()
            .addGap(87, 87, 87)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(tmark1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(lmark1))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(tmark2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(lmark2))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addComponent(ltotal)
                .addComponent(ttotal, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addContainerGap(131, Short.MAX_VALUE))
    );

    pack();
}// </editor-fold>

private void ttotalActionPerformed(java.awt.event.ActionEvent evt) {

}

/**
* @param args the command line arguments
*/
public static void main(String args[]) {
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new example2().setVisible(true);
        }
    });
}

// Variables declaration - do not modify
private javax.swing.JLabel lmark1;
private javax.swing.JLabel lmark2;
private javax.swing.JLabel ltotal;
public javax.swing.JTextField tmark1;
public javax.swing.JTextField tmark2;
public javax.swing.JTextField ttotal;
// End of variables declaration

}

Thanks