I faced a NullPointerException for below code. What is the cause?

import javax.swing.*; 
import java.awt.*; 
import java.awt.event.*; 
import net.sourceforge.jdatepicker.*; 
import net.sourceforge.jdatepicker.graphics.*; 
import net.sourceforge.jdatepicker.impl.*; 
import net.sourceforge.jdatepicker.util.*;
import java.text.DateFormat; 
import java.text.SimpleDateFormat;
import java.util.Calendar; 
import java.util.Date;
public class selectDate extends JFrame implements ActionListener
{
JLabel CheckDate; JButton check;
public UtilDateModel model;
public JDatePanelImpl datePanel;
public JDatePickerImpl datePicker;
public selectDate()
    {
    UtilDateModel model = new UtilDateModel();  
    JDatePanelImpl datePanel = new JDatePanelImpl(model);  
    JDatePickerImpl datePicker = new JDatePickerImpl(datePanel);
    JPanel panel=new JPanel();
    CheckDate=new JLabel("Date:");
    check=new JButton("CHECK"); 
    check.addActionListener(this);
    panel.add(CheckDate);
    panel.add(datePicker);
    panel.add(check);
    add(panel);
    setBounds(200,150,400,300);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setResizable(false);
    setVisible(true); 
    }
public void actionPerformed(ActionEvent e) 
    {if(check==e.getSource())
    {
    Date selectedDate = (Date) datePicker.getModel().getValue();
    DateFormat df = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss");
    String reportDate = df.format(selectedDate);
    JOptionPane.showMessageDialog(null,reportDate);
    }}
public static void main(String args[])
{new selectDate();}
}

Hi!

in your code

public UtilDateModel model;   // global variable 
public JDatePanelImpl datePanel;
public JDatePickerImpl datePicker;
public selectDate()
    {
    UtilDateModel model = new UtilDateModel();  // local variable
    JDatePanelImpl datePanel = new JDatePanelImpl(model);  
    JDatePickerImpl datePicker = new JDatePickerImpl(datePanel

in above you twise created object with same name and refer the empty object only,

please correct your code as

public UtilDateModel model;   // global variable declaration
    public JDatePanelImpl datePanel;
    public JDatePickerImpl datePicker;
    public selectDate()
        {
        model = new UtilDateModel();  
        datePanel = new JDatePanelImpl(model);  
        datePicker = new JDatePickerImpl(datePanel

Now try to use this..,

Have A Happy Day..,

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