Use JFormattedTextField to accept IP address only in Java

//  w  w w .  ja  v a 2s .  c  o  m
import java.awt.Container;
import java.text.ParseException;
import java.util.StringTokenizer;

import javax.swing.BoxLayout;
import javax.swing.JFormattedTextField;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.text.DefaultFormatter;

public class Main {
  public static void main(String args[]) throws ParseException {
    JFrame f = new JFrame();
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    Container content = f.getContentPane();
    content.setLayout(new BoxLayout(content, BoxLayout.PAGE_AXIS));

    JFormattedTextField ftf1 = new JFormattedTextField(new IPAddressFormatter());
    content.add(ftf1);

    
    content.add(new JTextField());
    f.setSize(300, 100);
    f.setVisible(true);
  }
}
/**
 * A formatter for 4-byte IP addresses of the form a.b.c.d
 */
class IPAddressFormatter extends DefaultFormatter
{
   public String valueToString(Object value) throws ParseException
   {
      if (!(value instanceof byte[])) throw new ParseException("Not a byte[]", 0);
      byte[] a = (byte[]) value;
      if (a.length != 4) throw new ParseException("Length != 4", 0);
      StringBuilder builder = new StringBuilder();
      for (int i = 0; i < 4; i++)
      {
         int b = a[i];
         if (b < 0) b += 256;
         builder.append(String.valueOf(b));
         if (i < 3) builder.append('.');
      }
      return builder.toString();
   }

   public Object stringToValue(String text) throws ParseException
   {
      StringTokenizer tokenizer = new StringTokenizer(text, ".");
      byte[] a = new byte[4];
      for (int i = 0; i < 4; i++)
      {
         int b = 0;
         if (!tokenizer.hasMoreTokens()) throw new ParseException("Too few bytes", 0);
         try
         {
            b = Integer.parseInt(tokenizer.nextToken());
         }
         catch (NumberFormatException e)
         {
            throw new ParseException("Not an integer", 0);
         }
         if (b < 0 || b >= 256) throw new ParseException("Byte out of range", 0);
         a[i] = (byte) b;
      }
      if (tokenizer.hasMoreTokens()) throw new ParseException("Too many bytes", 0);
      return a;
   }
}