A calculator programe, I want to use NumberPad to calculate

Question

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
class calculatorPanel extends JPanel implements ActionListener{
     private boolean first = true;
     private int result =0;
     private String op = "=";
     private JTextField screen;
     public calculatorPanel(){
          setLayout(new BorderLayout());
          screen = new JTextField(10);             //
//          screen.setEditable(false);
          screen.setHorizontalAlignment(JTextField.RIGHT);
/*          screen.addKeyListener(new KeyAdapter(){
               public void KeyTyped(KeyEvent e){
                    String s = "";
                    char c = e.getKeyChar();
                    if(c >= '0' && c <= '9'){
                         if(first){     
                              screen.setText(s+c);
                         else
                              screen.setText(screen.getText()+c);
                         first = false;
                    else{
                         if(first){
                              if(c == '-'){
                                   screen.setText(s+c);
                                  first = false;
                              else{
                                   op = s;
                         else{
                              String t = screen.getText();
                               int x = Integer.parseInt(t.substring(0,t.length()-1));
                               calculate(x);
                               op = s+c;
                               first = true;
                         if(c == 'c'){
                              screen.setText("0");
                              result = 0;
                              first = true;
                              op = "=";
          add(screen,"North");
          JPanel p = new JPanel();                         //??????????????????
          p.setLayout(new GridLayout(4,4,5,5));          //
          String buttons = "789/456*123-0c=+";          //
          for(int i=0;i < buttons.length();i++)          //
               addButton(p,buttons.substring(i,i+1));
          add(p,"Center");
     private void addButton(Container c,String s){
          JButton b = new JButton(s);
          c.add(b);
          b.setBorder(BorderFactory.createBevelBorder(BevelBorder.RAISED));
          b.addActionListener(this);
//          b.addKeyListener(new KeyAdapter());
     public void actionPerformed(ActionEvent e){
          String s = e.getActionCommand();
          if(s.charAt(0) >= '0' && s.charAt(0) <= '9'){
               if(first)     screen.setText(s);
               else
                    screen.setText(screen.getText()+s);
                    first = false;
          else{
               if(first){
                    if(s.equals("-")){
                         screen.setText(s);
                        first = false;
                    else op = s;
               else{
                int x = Integer.parseInt(screen.getText());
                calculate(x);
                op = s;
                first = true;
               if(s.equals("c")){
                    screen.setText("0");
                    result = 0;
                    first = true;
                    op = "=";
     public void calculate(int n){
          if(op.equals("+")) result += n;
               else if (op.equals("-")) result -= n;
               else if (op.equals("*")) result *= n;
               else if (op.equals("/")) result /= n;
               else if (op.equals("=")) result  = n;
               screen.setText(""+result);
class calculatorFrame extends JFrame{
     public calculatorFrame(){
          setTitle("Calculator");
          setSize(200,200);
          Container contentPane = getContentPane();
          contentPane.add(new calculatorPanel());
          addWindowListener(new WindowAdapter(){//
               public void windowClosing(WindowEvent e){
                    System.exit(0);
public class calculator{
     public static void main(String args[]){
          JFrame frame = new calculatorFrame();
          frame.show();
//          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//          frame.setVisible(true);
//          frame.pack();
}

Answer 1

So what is your problem?
One obvious thing is that in your commented out code you have a method
public void KeyTyped(KeyEvent e){
but if you are expecting this to be invoked when a key is pressed then you will be disappointed. The method name should probably be 'keyPressed' or maybe 'keyReleased'.