java只打印一次总值，无需迭代

Question

我想打印语句System.out.println(sb.append(ss));

直到最后一次我试图将其从for循环中取出，但结果是错误的

 public static String constatmentvertBinaryStringToString(String string) {
    StringBuilder sb = new StringBuilder();
    char[] chars = string.toCharArray();
    String ss = null;

    //for each character
    for (int j = 0; j < chars.length; j += 8) {
        int idx = 0;
        int sum = 0;
        //for each bit in reverse
        for (int i = 7; i >= 0; i--) {
            if (chars[i + j] == '1') {
                sum += 1 << idx;
            }
            idx++;
        }
        System.out.println(sum); //debug
        int div = sum / 4;
        System.out.println(div);
        System.out.println((char) div);
        int rem = sum % 4;
        System.out.println(rem);
        ss = (char) div + "" + rem;
        System.out.println(sb.append(ss));
    }
    return sb.toString();
}