CODEWITHSUNDEEP
javahexjava.util.scanner
yageek
yageek

Reputation: 4455

Converting a string of hexadecimal valiues into an array of bytes using Scanner in Java

I would like to convert a string with the form "AA BB CC" or "0xAA 0xBB 0xCC" to an array of bytes. Reading the documentation of Scanner looked promising.

I assumed that hasNextByte() and getNextByte() would do the job but in fact not byte seems to be detected. The code is pretty simple:

byte[] bytesFromString(String value) {

    List<Byte> list = new ArrayList<>();
    Scanner scan = new Scanner(value);
    while(scan.hasNextByte(16)) {
     list.add(scan.nextByte(16));
    }

    byte[] bytes = new byte[list.size()];
    for(int i = 0; i < list.size(); i++){
        bytes[i] = list.get(i);
    }
    return bytes;
}

I always receive an empty array as output: hasNextByte(16) never detects the byte.

Any particular reason why it is not working?

Upvotes: 0

Views: 193

Answers (1)

Jorn Vernee
Jorn Vernee

Reputation: 33875

The problem is that your values (AA BB and CC) are out of range for byte, since byte is signed.

A possible workaround is to read the values as short and then cast to byte:

while (scan.hasNextShort(16)) {
    list.add((byte) scan.nextShort(16));
}

Printing the results, you will see that the values are negative:

String input = "AA BB CC";
byte[] result = bytesFromString(input);
System.out.println(Arrays.toString(result)); // [-86, -69, -52]

Showing the overflow.

Upvotes: 1

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