To Convert StringBuffer To A Byte Array In Java

Question

I have a StringBuffer,strbuf=161656070200000000202020202001000000009E52;.

I want to convert into a byte array that looks like this:

byte[] byte_array=new byte[]
 {(byte)0x16,(byte)0x16,(byte)0x56,(byte)0x07,
  (byte)0x02,(byte)0x00,(byte)0x00,(byte)0x00,
  (byte)0x00,(byte)0x20,(byte)0x20,(byte)0x20,
  (byte)0x20,(byte)0x20,(byte)0x01,(byte)0x00,
  (byte)0x00,(byte)0x00,(byte)0x00,(byte)0x9E,(byte)0x52};

Do I need to convert strbuf to hex string and then do getBytes()? What is the right approach to this problem?

Peter Lawrey · Accepted Answer · 2011-11-18 11:23:07Z

8

You can try the following.

final String longHex = "161656070200000000202020202001000000009E52";
byte[] bytes = new BigInteger(longHex, 16).toByteArray();
System.out.println(Arrays.toString(bytes));

prints

[22, 22, 86, 7, 2, 0, 0, 0, 0, 32, 32, 32, 32, 32, 1, 0, 0, 0, 0, -98, 82]

answered Nov 18, 2011 at 11:23

Peter Lawrey

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Comments

Andrzej Doyle · Accepted Answer · 2011-11-18 11:23:50Z

5

Let's break the problem down, and work backwards here.

Do you know:

How to convert an int into a byte (assuming the former is in range)?
How to convert a two-character String into an int?
How to convert a long String into chunks of two characters each?

I suspect that you are able to do any of these tasks individually. Simply doing all of them in sequence (in reverse order) will yield the solution you're looking for.

</teaching-to-fish>

answered Nov 18, 2011 at 11:23

Andrzej Doyle

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3 Comments

S.K Over a year ago

instead of asking me what i know, i think it would be better if you explain us in your "systematic" way..

Andrzej Doyle Over a year ago

Perhaps. But merely giving you a chunk of code will let you copy-paste, move on, and then come back to SO next time you get stuck. Instead, leading you through the steps required to realise the solution on your own is more time-consuming, but means you can resolve similar problems yourself in future - which makes you a better developer.

S.K Over a year ago

i dont know what to say. Since i couldnt find a solution, i posted this question. And thank u very much..

John B · Accepted Answer · 2011-11-18 11:25:08Z

0

String longHex = "....";
byte[] array = new byte[longHex.length() / 2];
for (int i=0; i<array.length; i++){
     Byte byte = Byte.parseByte(longHex.substring(i*2, i*2+2), 16);
     array[i] = byte;
}

answered Nov 18, 2011 at 11:25

John B

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