Convert a string representation of a hex dump to a byte array using Java?

Question

I am looking for a way to convert a long string (from a dump), that represents hex values into a byte array.

I couldn't have phrased it better than the person that posted the same question here.

But to keep it original, I'll phrase it my own way: suppose I have a string "00A0BF" that I would like interpreted as the

byte[] {0x00,0xA0,0xBf} 

what should I do?

I am a Java novice and ended up using BigInteger and watching out for leading hex zeros. But I think it is ugly and I am sure I am missing something simple.

Answer 1

Update (2021) - Java 17 now includes java.util.HexFormat (only took 25 years):

HexFormat.of().parseHex(s)

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For older versions of Java:

Here's a solution that I think is better than any posted so far:

/* s must be an even-length string. */ public static byte[] hexStringToByteArray(String s) {     int len = s.length();     byte[] data = new byte[len / 2];     for (int i = 0; i < len; i += 2) {         data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4)                              + Character.digit(s.charAt(i+1), 16));     }     return data; } 

Reasons why it is an improvement:

• Safe with leading zeros (unlike BigInteger) and with negative byte values (unlike Byte.parseByte)

• Doesn't convert the String into a char[], or create StringBuilder and String objects for every single byte.

• No library dependencies that may not be available

Feel free to add argument checking via assert or exceptions if the argument is not known to be safe.