Convert int to hex byte value

Question

I want to read block wise data of NFC tag. For which the command is a byte array and it needs block number.

public static byte[] readSingleBlockCmd(int blockNo) {
        byte[] cmd = new byte[3];
        cmd[0] = (byte) 0x02;//flag
        cmd[1] = (byte) 0x23;//cmd
        cmd[2]= (byte)blockNo;

        return cmd;

    }

How can I change the int blockNo to its hexadecimal value , which can be cast to byte .I want the byte value and not an byte []

I have gone through the following links

Convert integer into byte array (Java)

How to autoconvert hexcode to use it as byte[] in Java?

Java integer to byte array

Thanks!

Isn't your question answered by those links? If not, update your question to explain why and what you are having trouble with specifically. — Radiodef
– Radiodef, Commented May 26, 2015 at 17:20
Let's clear some things up: "Hexadecimal" is an encoding, specifically for how to write the number out as a String. 0x25 is hexadecimal encoded. But the number itself is still 37 (in base 10), and it is an int or a byte or whatever. You're not using any Strings here, so please forget about the "hexadecimal" part of your question and please ask again, because I don't know what you have in mind. — dcsohl
– dcsohl, Commented May 26, 2015 at 17:28

Anindya Dutta · Accepted Answer · 2015-05-26 17:28:24Z

3

Converting an integer (in decimal) to hex can be done with the following line:

String hex = Integer.toHexString(blockNo);

Then to convert it to byte, you can use

Byte.parseByte(hex,16);

But if all you wanted to do is convert the parameter to bytes:

Byte.parseByte(blockNo);

would work too I guess. Correct me if I'm wrong.

answered May 26, 2015 at 17:28

Anindya Dutta

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1 Comment

Anindya Dutta Over a year ago

Exactly, it's supposed to do nothing. it is the same as the last line that I mentioned. But since he wants a hexadecimal, I suggested that he could do it with the inbuilt function to convert to into a string.

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