Hex-encoded String to Byte Array

Question

String str = "9B7D2C34A366BF890C730641E6CECF6F"; 

I want to convert str into byte array, but str.getBytes() returns 32 bytes instead of 16.

Answer 1

I think what the questioner is after is converting the string representation of a hexadecimal value to a byte array representing that hexadecimal value.

The apache commons-codec has a class for that, Hex.

String s = "9B7D2C34A366BF890C730641E6CECF6F";     byte[] bytes = Hex.decodeHex(s.toCharArray()); 

Answer 2

Java SE 6 or Java EE 5 provides a method to do this now so there is no need for extra libraries.

The method is DatatypeConverter.parseHexBinary

In this case it can be used as follows:

String str = "9B7D2C34A366BF890C730641E6CECF6F"; byte[] bytes = DatatypeConverter.parseHexBinary(str); 

The class also provides type conversions for many other formats that are generally used in XML.