class MyRegex {
    String pattern = "(((25[0-5])|(2[0-4]\\d)|([0-1]?\\d{1,2}))(\\.|$)){4}";
}

class MyRegex
{
    static String pattern="^(([01]?[0-9]{0,2})|((2[0-4][0-9])|(25[0-5])))\\.(([01]?[0-9]{0,2})|((2[0-4][0-9])|(25[0-5])))\\.(([01]?[0-9]{0,2})|((2[0-4][0-9])|(25[0-5])))\\.(([01]?[0-9]{0,2})|((2[0-4][0-9])|(25[0-5])))$";
}

class MyRegex{
    static String pattern="^((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$";
}

// 25[0-5] matches 250-255
// 2[0-4]\d matches 200-249 
// [0-1]?\d{1,2} matches 0-199 with or without leading 0s
// \.|$ matches period or end-of-line after each of the above number group matches
// {4} requres the above (number w/ period | number w/ eol) match exaclty 4 times
String pattern = "(((25[0-5])|(2[0-4]\\d)|([0-1]?\\d{1,2}))(\\.|$)){4}";