import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
 
public class DataFrame extends JFrame
{
    protected DataPanel panel = new DataPanel();
    public static void main(String[] args)
    {
        DataFrame df = new DataFrame();
        df.setVisible(true);
    }
 
    public DataFrame()
    {
        super("Enter Data");
        buildLayout();
        pack();
    }
 
    protected void buildLayout()
    {
        Container pane = getContentPane();
        pane.setLayout(new BorderLayout());
        pane.add(new DataPanel(),BorderLayout.CENTER);
        JButton button = new JButton("Ok");
        button.addActionListener(new ActionListener()
            {
                public void actionPerformed(ActionEvent event)
                {
                    onOk();
                }
            });
 
            JPanel panel = new JPanel();
            panel.setLayout(new FlowLayout(FlowLayout.CENTER,0,0));
            panel.add(button);
            pane.add(panel,BorderLayout.SOUTH);
        }
 
        protected void onOk()
        {
            try
            {
                panel.validateInput();
                System.exit(0);
            }
            catch(InputValidationException ive)
            {
                ive.errorSource.requestFocus();
                JOptionPane.showMessageDialog(this,ive.getMessage(),
                                              "Validation Error",
                                               JOptionPane.ERROR_MESSAGE);
           }
        }
 
    }

import java.awt.GridLayout;
import javax.swing.*;
 
public class DataPanel extends JPanel
{
    protected JTextField nameField;
    protected JTextField ageField;
 
    public DataPanel()
    {
        buildDisplay();
    }
 
    public void validateInput() throws InputValidationException
    {
        String name = nameField.getText();
        if(name.length() == 0)
        {
            throw new InputValidationException("No name was spefified",nameField);
        }
        String age=ageField.getText();
        try
        {
            int value=Integer.parseInt(age);
            if(value <= 0)
            {
                throw new InputValidationException("Age value must be " + "a positive integer",ageField);
            }
        }
        catch(NumberFormatException e)
        {
            throw new InputValidationException("Age value is missing " +
                                                "or invalid",ageField);
        }
    }
    protected void buildDisplay()
    {
        setLayout(new GridLayout(2,2,10,5));
        JLabel label = new JLabel("Name: ");
        add(label);
        nameField = new JTextField(10);
        add(nameField);
        label = new JLabel("Age:");
        add(label);
        ageField=new JTextField(10);
        add(ageField);
    }
}

import java.awt.Component;
 
public class InputValidationException extends Exception
{
    protected Component errorSource;
 
    public InputValidationException(String message,Component source)
    {
        super(message);
        errorSource = source;
    }
}

protected DataPanel panel = new DataPanel();

pane.add(new DataPanel(),BorderLayout.CENTER);