convert hexString To Byte Array

encode_decode.java

public static byte[] convertToByteArray(String hexString) {
        int len = hexString.length();
        byte[] data = new byte[(len / 2)];
        for (int i = 0; i < len; i += 2) {
            data[i / 2] = (byte) ((Character.digit(hexString.charAt(i), 16) << 4) + Character.digit(hexString.charAt(i + 1), 16));
        }
        return data;
    }