Java正则匹配提取年月日字符串

String string1="9999-9-99";
        Pattern p = Pattern.compile("(\\d{4})-(\\d{1,2})-(\\d{1,2})");
        Matcher m = p.matcher(string1);
        if(m.find()) {
            System.out.println(m.group());
            System.out.println(m.group(0));
            System.out.println(m.group(1));
            System.out.println(m.group(2));
            System.out.println(m.group(3));
        }