Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!eu.feeder.erje.net!news.albasani.net!.POSTED!not-for-mail
From: Laura Schmidt <ls@mailinator.com>
Newsgroups: comp.lang.java.programmer
Subject: Re: convert byte array to hex string using BigInteger
Date: Thu, 20 Jun 2013 15:32:56 +0200
Organization: albasani.net
Lines: 27
Message-ID: <kpv0a9$gio$1@news.albasani.net>
References: <kpur29$5v4$1@news.albasani.net> <9hv5s85cul11v42sfop0388joag6mu6t4e@4ax.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
X-Trace: news.albasani.net nNmLG4MIHWHG0DXLdQiI86nOobXHJ27SHSvEOGD3Ua5VZWhYhevYmabaJrGCnciswPOU7C+QtXLw8HENM6GTH/IYCmzwGUlfzTDg2dVnQhjumICDZyPe7yd6ine8/mq4
NNTP-Posting-Date: Thu, 20 Jun 2013 13:32:57 +0000 (UTC)
Injection-Info: news.albasani.net; logging-data="P5O5efvJ+3TXkPitwJEiMLrAzEhkvfkVZ/le8Y7+N7uwR9L4aUj2+N8JdqhV0+3UJzpiMDpVRiepDaHPgl4Oa1pLR1aIO+nTkzduSTpNtj7cxRMwSIClAp3eERDdWusF"; mail-complaints-to="abuse@albasani.net"
User-Agent: Mozilla/5.0 (X11; Linux i686; rv:10.0.12) Gecko/20130116 Icedove/10.0.12
In-Reply-To: <9hv5s85cul11v42sfop0388joag6mu6t4e@4ax.com>
Cancel-Lock: sha1:MokL3Cmd7+mQuEooH1sfDXcTByQ=
Xref: csiph.com comp.lang.java.programmer:24485

On 06/20/2013 03:09 PM, rossum wrote:

> This is a case of RTFM.  The Javadocs for BigInteger(byte[]) tell you
> that it expects the byte array in two's complement representation, so
> a leading 1 bit is interpreted as a negative number.  You need a
> different constructor:
>
>    public BigInteger(int signum, byte[] magnitude)

You are right, sorry.

Now I get a hex string without sign. But now the decode method does not 
return the original bytes anymore:

  private byte [] hex_decode (String val)
  {
   BigInteger b = new BigInteger (val,16);
   byte [] t = b.toByteArray();

   return (t);
  }

There is no other constructor for byte arrays.
And I don't really understand why it doesn't return the original byte array.

Laura