CODEWITHSUNDEEP
javac
rikkima
rikkima

Reputation: 95

Java convert hex string to java: char[] (C) to byte[] (JAVA)

How to convert hex string in java that keep the same values.

In C i have:

char tab[24] = { 0x02, 0x04, 0xF3, 0xFC, 0xFF, 0x06, 0x00, 0xF7, 0x00, 0x00, 0x09, 0xFD, 0xFD, 0x00, 0x03, 0x0A, 0xFD, 0x02, 0xFD, 0x08, 0x08, 0x00, 0x01, 0xFD };

And i copy to java like a string;

String hexString = "0x02, 0x04, 0xF3, 0xFC, 0xFF, 0x06, 0x00, 0xF7, 0x00, 0x00, 0x09, 0xFD, 0xFD, 0x00, 0x03, 0x0A, 0xFD, 0x02, 0xFD, 0x08, 0x08, 0x00, 0x01, 0xFD";

Now i want to convert in byte[], i find some ways how to do it but it looks like i do not convert in right format.

SOLVED

String[] split = hexString.split(", ");       
byte[] arr = new byte[split.length];
for (int i = 0; i < split.length; i++)
{
    arr[i] = (byte)(short)Short.decode(split[i]);
}

Upvotes: 3

Views: 8915

Answers (3)

Joni
Joni

Reputation: 111269

What you have in C would be this in Java:

byte[] tab = { 0x02, 0x04, (byte) 0xF3, (byte) 0xFC, (byte) 0xFF, 0x06, 
               0x00, (byte) 0xF7, 0x00, 0x00, 0x09, (byte) 0xFD, (byte) 0xFD, 
               0x00, 0x03, 0x0A, (byte) 0xFD, 0x02, (byte) 0xFD, 0x08, 
               0x08, 0x00, 0x01, (byte) 0xFD };

Note that instead of char you use byte, and that values that are outside of the allowed range for byte such as 0xFD need an explicit cast. And you don't include the array length in the declaration.

Update: To not add casts manually you can declare the data of a wider type (like int or short) and then loop over it:

int[] temp = { ... };
byte[] tab = new byte[temp.length];
for (int i = 0; i<temp.length; i++) tab[i]=(byte)temp[i];

A better solution would be loading the data from an external file though. Big array literals are not encoded into class files in a compact way like C compilers encode big array literals.

Upvotes: 2

rocketboy
rocketboy

Reputation: 9741

@Joni has the right answer. But if you want to do this on runtime you can do something like:

    String hex = "0xFFFFFFFF";
    long longRep = Long.decode(hex);
    byte[] byteRep = String.valueOf(intrRep).getBytes("UTF-8");

    //to verify
    System.out.println(Long.toHexString(Long.valueOf(new String(byteRep,"UTF-8"))));

Upvotes: 0

Bernhard Barker
Bernhard Barker

Reputation: 55609

If you actually want to convert the given string to a byte[] (though this seems like a strange requirement)...

String hexString = "0x02, 0x04, 0xF3, 0xFC, 0xFF, 0x06, 0x00, 0xF7, 0x00, 0x00, 0x09, 0xFD, 0xFD, 0x00, 0x03, 0x0A, 0xFD, 0x02, 0xFD, 0x08, 0x08, 0x00, 0x01, 0xFD";
String[] split = hexString.split(", ");
byte[] arr = new byte[split.length];
for (int i = 0; i < split.length; i++)
{
   arr[i] = (byte)Short.parseShort(split[i].substring(2), 16);
}
System.out.println(Arrays.toString(arr));

We need to use parseShort instead of parseByte because trying to parse something like 0xF3 with parseByte causes NumberFormatException: Value out of range.

Prints:

[2, 4, -13, -4, -1, 6, 0, -9, 0, 0, 9, -3, -3, 0, 3, 10, -3, 2, -3, 8, 8, 0, 1, -3]

Upvotes: 4

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