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Groups > comp.lang.java.programmer > #24492

Re: convert byte array to hex string using BigInteger

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lipska the kat wrote:
> Laura Schmidt wrote:
>> 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.
> 
> I'm not sure what all this twos compliment stuff is about

That's spelled "two's-complement".

> twos compliment is just a number representation scheme

And the purpose of that constructor is just to convert a representation 
in that scheme to the correct number.

> There should be no need to 'convert' anything

If there isn't, then don't use that constructor.

-- 
Lew

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Thread

convert byte array to hex string using BigInteger Laura Schmidt <ls@mailinator.com> - 2013-06-20 14:03 +0200
  Re: convert byte array to hex string using BigInteger Eric Sosman <esosman@comcast-dot-net.invalid> - 2013-06-20 09:03 -0400
  Re: convert byte array to hex string using BigInteger rossum <rossum48@coldmail.com> - 2013-06-20 14:09 +0100
    Re: convert byte array to hex string using BigInteger Laura Schmidt <ls@mailinator.com> - 2013-06-20 15:32 +0200
      Re: convert byte array to hex string using BigInteger rossum <rossum48@coldmail.com> - 2013-06-20 15:44 +0100
      Re: convert byte array to hex string using BigInteger lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-06-20 19:22 +0100
        Re: convert byte array to hex string using BigInteger markspace <markspace@nospam.nospam> - 2013-06-20 11:56 -0700
          Re: convert byte array to hex string using BigInteger lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-06-20 20:43 +0100
        Re: convert byte array to hex string using BigInteger Lew <lewbloch@gmail.com> - 2013-06-20 13:39 -0700
          Re: convert byte array to hex string using BigInteger lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-06-21 08:17 +0100
        Re: convert byte array to hex string using BigInteger Arne Vajhøj <arne@vajhoej.dk> - 2013-06-26 22:16 -0400
  Re: convert byte array to hex string using BigInteger Joerg Meier <joergmmeier@arcor.de> - 2013-06-20 22:09 +0200
  Re: convert byte array to hex string using BigInteger Roedy Green <see_website@mindprod.com.invalid> - 2013-06-21 14:51 -0700
    Re: convert byte array to hex string using BigInteger Joerg Meier <joergmmeier@arcor.de> - 2013-06-22 00:26 +0200
      Re: convert byte array to hex string using BigInteger Roedy Green <see_website@mindprod.com.invalid> - 2013-06-23 08:49 -0700
        Re: convert byte array to hex string using BigInteger Joerg Meier <joergmmeier@arcor.de> - 2013-06-23 22:37 +0200
      Re: convert byte array to hex string using BigInteger Roedy Green <see_website@mindprod.com.invalid> - 2013-06-23 12:40 -0700
        Re: convert byte array to hex string using BigInteger Joerg Meier <joergmmeier@arcor.de> - 2013-06-23 22:41 +0200
  Re: convert byte array to hex string using BigInteger Arne Vajhøj <arne@vajhoej.dk> - 2013-06-26 22:12 -0400
    Re: convert byte array to hex string using BigInteger Arne Vajhøj <arne@vajhoej.dk> - 2013-06-26 22:20 -0400
    Re: convert byte array to hex string using BigInteger Laura Schmidt <ls@mailinator.com> - 2013-06-28 07:55 +0200
      Re: convert byte array to hex string using BigInteger Joerg Meier <joergmmeier@arcor.de> - 2013-06-29 00:01 +0200
    Re: convert byte array to hex string using BigInteger Stanimir Stamenkov <s7an10@netscape.net> - 2013-06-29 19:10 +0300
      Re: convert byte array to hex string using BigInteger Arne Vajhøj <arne@vajhoej.dk> - 2013-07-03 22:24 -0400
  Re: convert byte array to hex string using BigInteger aydin.k.abadi@gmail.com - 2013-11-23 16:40 -0800
  Re: convert byte array to hex string using BigInteger aydin.k.abadi@gmail.com - 2013-11-23 16:43 -0800
    Re: convert byte array to hex string using BigInteger Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2013-11-24 10:43 +0000

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