Convert a string representation of a hex dump to a byte array using Java?
Solution 1:
Update (2021) - Java 17 now includes java.util.HexFormat
(only took 25 years):
HexFormat.of().parseHex(s)
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.
Solution 2:
One-liners:
import javax.xml.bind.DatatypeConverter;
public static String toHexString(byte[] array) {
return DatatypeConverter.printHexBinary(array);
}
public static byte[] toByteArray(String s) {
return DatatypeConverter.parseHexBinary(s);
}
Warnings:
- in Java 9 Jigsaw this is no longer part of the (default) java.se root
set so it will result in a ClassNotFoundException unless you specify
--add-modules java.se.ee (thanks to @
eckes
) - Not available on Android (thanks to
Fabian
for noting that), but you can just take the source code if your system lacksjavax.xml
for some reason. Thanks to @Bert Regelink
for extracting the source.
Solution 3:
The Hex class in commons-codec should do that for you.
http://commons.apache.org/codec/
import org.apache.commons.codec.binary.Hex;
...
byte[] decoded = Hex.decodeHex("00A0BF");
// 0x00 0xA0 0xBF