the programe is basic Calculator , i add new Class extends the
Calculator class add Override method inside method i use
Super.createPanel then i want add text Filed in this Method return in
runtime NotllPointer Wxception
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class CCalculator1 extends JFrame {
    // to use in sub class
    private Container con = new Container ();
    //
    private JPanel tpanel = new JPanel ();
    private JPanel bpanel = new JPanel();
    private JPanel npanel = new JPanel ();
    private JPanel pluspanel = new JPanel ();
    private JPanel equalpanel = new JPanel ();
    private JPanel clearpanel = new JPanel ();
    private JPanel advpanel = new JPanel ();
    protected JTextField text = new JTextField();
    private String label [] =
    { "7","8","9","4","5","6","1","2" ,"3 ","0","."," -/+ ","/","*","-",
        "+","C","="};
    private String advlabel [] =
    {"PI","E","sqr","Sin","Cos",
        "Tan","Log","Log10","a^2"};
    private JButton advbutton [] = new JButton [advlabel.length];
    private JButton button [] = new JButton [label.length];
    private String str1 = new String ("0");
    private String str2 = new String ("");
    private String str3 = new String ("");
    private String pi = new String ("");
    private float var1  =0;
    private float var2 =0;

    CCalculator1 (){
        try {
            this.jbinit ();
        }
        catch (Exception e ){
            e.printStackTrace();
        }
    }

    protected void jbinit () throws Exception{

        // Set Content
        this.con = getContentPane ();
        this.con.setLayout(null);

        // Panel
        this.createPanel ();

        // Frame
        this.setTitle("Calcultor");
        this.setSize(new Dimension (400,400));
        this.setLocation(new Point (300,400));
        this.setVisible(true);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    }

    protected void createPanel () {

        // Set Panel
        tpanel.setLayout(new BorderLayout ());
        tpanel.setSize(new Dimension (270,30));
        tpanel.setLocation(new Point (10,10));
        tpanel.setOpaque(true);
        tpanel.setBorder(BorderFactory.createLineBorder(Color.BLACK));

        // Set Panel
        bpanel.setLayout(new GridLayout (4,3));
        bpanel.setSize(new Dimension (270,100));
        bpanel.setLocation(new Point (10,50));
        bpanel.setOpaque(true);
        bpanel.setBorder(BorderFactory.createLineBorder(Color.BLACK));

        // Set Panel *,,/,-
        npanel.setLayout(new GridLayout (1,3));
        npanel.setSize(new Dimension (270,30));
        npanel.setLocation(new Point (10,155));
        npanel.setOpaque(true);
        npanel.setBorder(BorderFactory.createLineBorder(Color.BLACK));

        // Set Panel
        pluspanel.setLayout(new GridLayout (1,1));
        pluspanel.setSize(new Dimension (60,100));
        pluspanel.setLocation(new Point (290,50));
        pluspanel.setOpaque(true);
        pluspanel.setBorder(BorderFactory.createLineBorder(Color.BLACK));

        // Set Panel
        equalpanel.setLayout(new GridLayout (1,1));
        equalpanel.setSize(new Dimension (60,30));
        equalpanel.setLocation(new Point (290,155));
        equalpanel.setOpaque(true);
        equalpanel.setBorder(BorderFactory.createLineBorder(Color.BLACK));

        // Set Panel
        clearpanel.setLayout(new GridLayout (1,1));
        clearpanel.setSize(new Dimension (60,30));
        clearpanel.setLocation(new Point (290,10));
        clearpanel.setOpaque(true);
        clearpanel.setBorder(BorderFactory.createLineBorder(Color.BLACK));

        // Set Panel
        advpanel.setLayout(new GridLayout (3,3));
        advpanel.setSize(new Dimension (270,100));
        advpanel.setLocation(new Point (10,200));
        advpanel.setOpaque(true);
        advpanel.setBorder(BorderFactory.createLineBorder(Color.BLACK));

        // Text Field
        text.setText(str1);
        text.setColumns(20);
        text.setEditable(true);
        text.setHorizontalAlignment(JTextField.CENTER);

        //Add Componant
        tpanel.add(text);
        this.con.add(tpanel);

        //Add Componant Button Number
        for ( int i = 0 ; i < 12 ; i++){
            button [i] = new JButton ();
            button[i].setText(label[i]);
            bpanel.add(button[i]);
        }
        this.con.add(bpanel);

        //Add Componant - , * ,/
        for ( int i = 12 ; i < 15 ; i++){
            button [i] = new JButton ();
            button[i].setText(label[i]);
            npanel.add(button[i]);
        }
        this.con.add(npanel);

        //Add Componant  +
        button [15] = new JButton ();
        button[15].setText(label[15]);
        pluspanel.add(button[15]);
        this.con.add(pluspanel);

        //Add Componant  =
        button [17] = new JButton ();
        button[17].setText(label[17]);
        equalpanel.add(button[17]);
        this.con.add(equalpanel);

        //Add Componant  C
        button [16] = new JButton ();
        button[16].setText(label[16]);
        clearpanel.add(button[16]);
        this.con.add(clearpanel);

        //Add Advance Componant
        for ( int i = 0 ; i < advbutton.length ; i++){
            advbutton [i] = new JButton ();
            advbutton[i].setText(advlabel[i]);
            advpanel.add(advbutton[i]);
        }
        this.con.add(advpanel);
    }
}

Extends
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class AdvCCalculator extends CCalculator1 {

    public AdvCCalculator () {
    //    JOptionPane.showMessageDialog(null,"test"+con);

    }

    protected void createPanel () {
        super.createPanel();
        // set Panel
    }

    private void ceateAdvPanel (){
    }
    public static void main (String arg [] ) {
        AdvCCalculator c = new AdvCCalculator ();
    }
}

how to add Text Field in Panel Display in Frame