十进制转换二进制

// 十进制转换二进制
    private static String convertBinary(int sum) {
        StringBuffer binary = new StringBuffer();
        while (sum != 0 && sum != 1) {
            binary.insert(0, sum % 2);
            
            sum = sum / 2;
            if (sum == 0 || sum == 1) {
                binary.insert(0, sum % 2);
            }
        }
        return binary.toString();
    }