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String str = "9B7D2C34A366BF890C730641E6CECF6F"; I want to convert str into byte array, but str.getBytes() returns 32 bytes instead of 16.
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To convert hex string to byte array, you need to first get the length of the given string and include it while creating a new byte array. byte[] val = new byte[str. length() / 2]; Now, take a for loop until the length of the byte array.
Now, let's convert a hexadecimal digit to byte. As we know, a byte contains 8 bits. Therefore, we need two hexadecimal digits to create one byte.
Hexadecimal is used in the transfer encoding Base16, in which each byte of the plaintext is broken into two 4-bit values and represented by two hexadecimal digits.
A String is stored as an array of Unicode characters in Java. To convert it to a byte array, we translate the sequence of characters into a sequence of bytes. For this translation, we use an instance of Charset. This class specifies a mapping between a sequence of chars and a sequence of bytes.
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()); 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.
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