java字符串长度怎么算,java字符串长度

public static String addZeroForNum(String str, int strLength) { int strLen = str.length(); StringBuffer sb = null; while (strLen < strLength) { 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;}