[java] Java Regex IP Address and JTextField

import java.text.ParseException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

import javax.swing.text.DefaultFormatter;

public class RegexFormatter extends DefaultFormatter {
    private Pattern pattern;
    private Matcher matcher;

    public RegexFormatter() {
        super();
    }

    public RegexFormatter(String pattern) throws PatternSyntaxException {
        this();
        setPattern(Pattern.compile(pattern));
    }

    public RegexFormatter(Pattern pattern) {
        this();
        setPattern(pattern);
    }

    public void setPattern(Pattern pattern) {
        this.pattern = pattern;
    }

    public Pattern getPattern() {
        return pattern;
    }

    protected void setMatcher(Matcher matcher) {
        this.matcher = matcher;
    }

    protected Matcher getMatcher() {
        return matcher;
    }

    public Object stringToValue(String text) throws ParseException {
        Pattern pattern = getPattern();

        if (pattern != null) {
            Matcher matcher = pattern.matcher(text);

            if (matcher.matches()) {
                setMatcher(matcher);
                return super.stringToValue(text);
            }
            throw new ParseException("Pattern did not match", 0);
        }
        return text;
    }
}

String _255 = "(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)";
Pattern p = Pattern.compile( "^(?:" + _255 + "\\.){3}" + _255 + "$");
RegexFormatter ipFormatter = new RegexFormatter( p );
JFormattedTextField ipAddress = new JFormattedTextField( ipFormatter );

ipAddress.addPropertyChangeListener( "value",
    new PropertyChangeListener() {
        public void propertyChange( PropertyChangeEvent e ) {
           System.out.println( ipAddress.getValue() );
        }
    }
);