run mode :
               code for "-" button:
               private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {
               Double a,b,Result;
               a=Double.parseDouble(jTextField1.getText());
               b=Double.parseDouble(jTextField2.getText());
               Result=a-b;
               jTextField3.setText(Double.toString(Result));
                }
               RUn mode :