Convert a string representation of a number to binary format. For example "2" -> "00000010"

StringToBinary.java

private static String numToBin(String num) {
    BigInteger bi = new BigInteger(num);
    byte[] val = bi.toByteArray();
    StringBuilder sb = new StringBuilder();
    for (byte b: val) {
        sb.append(String.format("%8s", Integer.toBinaryString(b & 0xFF)).replace(' ', '0'));
    }
    sb.toString();
}