java字符追加问题

/**
*
*当传入的length长度小于传入字符串target的长度时，输出原有字符串
*/
public static String AppendPrefix(int length, String target, String append) {
StringBuffer sb = new StringBuffer();
int len = target.length();
for (int i = 0; i < length - len; i++) {
sb.append(append);
}
sb.append(target);
return sb.toString();
}