Converting a String of Bytes to a byte array

Question

I have a txt file, which is a String of Hex bytes separated by commas, for example:

0x01,0x02,0x03,0x04,0xA1,

I want to easily split this string by commas, and then have each Hex cast to a byte, but the only way I can get this working seems like a ludicrous amount of extra work.

Essentially I'm splitting into a String array, then having to loop through the String array to cast each individual "String" to a byte array using BigInteger, then looping through that byte array to cast it to a single byte and then adding that to a different byte array. Oh, and I have to manually remove the 0x from each "String" too.

String Data = "0x01,0x02,0x03,0x04,0xA1,";
String[] DataSplit = Data.split(",");
int DataLength = DataSplit.length;
byte[] byteArray = new byte[DataLength];

for(int i = 0; i < DataLength; i++) {

    String dataSingle = DataSplit[i].charAt(2) + "" + DataSplit[i].charAt(3); // remove 0x

    byte[] bytes = new BigInteger((dataSingle), 16).toByteArray();
    byte singleByte = 0;
    for (byte aByte : bytes) {
        singleByte += (byte) aByte;
    }

    byteArray[i] = (byte) singleByte;

}

This code works, but it's a stupid amount of code for such a basic process. This is being done in Android Studio for an Android App, but it's all Java

perhaps helpful to fly over this here: java-byte-arrays-hex-strings — Eritrean
– Eritrean, Commented Sep 16, 2021 at 13:12

Andy Turner · Accepted Answer · 2021-09-16 13:05:10Z

3

The loop is wildly over-complicated:

for(int i = 0; i < DataLength; i++) {
  byteArray[i] = (byte) Integer.parseInt(DataSplit[i].substring(2), 16);
}

(You need to use Integer.parseInt instead of Byte.parseByte in order to handle bytes greater than 0x7f).

edited Sep 16, 2021 at 13:05

answered Sep 16, 2021 at 12:59

Andy Turner

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