Java子网掩码转换网络位长度

public static int calcPrefixLengthByMack(String strip) {//输入子网掩码
        StringBuffer sbf;
        String str;
        // String strip = "255.255.255.240; // 子网掩码,结果 28
        int inetmask = 0, count = 0; 
        String[] ipList = strip.split("\\.");
        for (int n = 0; n < ipList.length; n++) {
            sbf = toBin(Integer.parseInt(ipList[n]));
            str = sbf.reverse().toString();



            // 统计2进制字符串中1的个数
            count = 0;
            for (int i = 0; i < str.length(); i++) {
                i = str.indexOf('1', i); // 查找 字符'1'出现的位置
                if (i == -1) {
                    break;
                }
                count++; // 统计字符出现次数
            }
            inetmask += count;
        }
        return inetmask;
    }


    public static StringBuffer toBin(int x) {
        StringBuffer result = new StringBuffer();
        result.append(x % 2);
        x /= 2;
        while (x > 0) {
            result.append(x % 2);
            x /= 2;
        }
        return result;
    }