如何实现java字符串格式化长度不足补0

System.out.println(String.format(“%09d”, 123);

System.out.println(String.format(“%9s”, “123″);

System.out.println(String.format(“%09d”, Long.parseLong(“123″)));

public static String addZeroForNum(String str, int strLength) {
    int strLen = str.length();
    if (strLen < strLength) {
        while (strLen < strLength) {
            StringBuffer sb = new StringBuffer();
            sb.append("0").append(str);// 左补0
            // sb.append(str).append("0");//右补0
            str = sb.toString();
            strLen = str.length();
        }
    }
    return str;
}