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From: Albretch Mueller on 27 Dec 2009 16:50
// __ http://www.rgagnon.com/javadetails/java-0596.html

The simple way
public static String getHexString(byte[] b) throws Exception {
String result = "";
for (int i=0; i < b.length; i++) {
result +=
Integer.toString( ( b[i] & 0xff ) + 0x100, 16).substring
( 1 );
}
return result;
}

A faster way
import java.io.UnsupportedEncodingException;

public class StringUtils {

static final byte[] HEX_CHAR_TABLE = {
(byte)'0', (byte)'1', (byte)'2', (byte)'3',
(byte)'4', (byte)'5', (byte)'6', (byte)'7',
(byte)'8', (byte)'9', (byte)'a', (byte)'b',
(byte)'c', (byte)'d', (byte)'e', (byte)'f'
};

public static String getHexString(byte[] raw)
throws UnsupportedEncodingException
{
byte[] hex = new byte[2 * raw.length];
int index = 0;

for (byte b : raw) {
int v = b & 0xFF;
hex[index++] = HEX_CHAR_TABLE[v >>> 4];
hex[index++] = HEX_CHAR_TABLE[v & 0xF];
}
return new String(hex, "ASCII");
}

public static void main(String args[]) throws Exception{
byte[] byteArray = {
(byte)255, (byte)254, (byte)253,
(byte)252, (byte)251, (byte)250
};

System.out.println(StringUtils.getHexString(byteArray));

/*
* output :
* fffefdfcfbfa
*/

}
}
From: Lew on 27 Dec 2009 17:11
Albretch Mueller wrote:
> // __ http://www.rgagnon.com/javadetails/java-0596.html
>
> The simple way
> public static String getHexString(byte[] b) throws Exception {
> String result = "";
> for (int i=0; i < b.length; i++) {
> result +=
> Integer.toString( ( b[i] & 0xff ) + 0x100, 16).substring
> ( 1 );
> }
> return result;
> }
>
> A faster way
> import java.io.UnsupportedEncodingException;
>
> public class StringUtils {
>
> static final byte[] HEX_CHAR_TABLE = {
> (byte)'0', (byte)'1', (byte)'2', (byte)'3',
> (byte)'4', (byte)'5', (byte)'6', (byte)'7',
> (byte)'8', (byte)'9', (byte)'a', (byte)'b',
> (byte)'c', (byte)'d', (byte)'e', (byte)'f'
> };
>
> public static String getHexString(byte[] raw)
> throws UnsupportedEncodingException
> {
> byte[] hex = new byte[2 * raw.length];
> int index = 0;
>
> for (byte b : raw) {
> int v = b & 0xFF;
> hex[index++] = HEX_CHAR_TABLE[v >>> 4];
> hex[index++] = HEX_CHAR_TABLE[v & 0xF];
> }
> return new String(hex, "ASCII");
> }
// ...
> }

You can avoid encoding and some obfuscation by making the table 'char []' and
using 'StringBuilder hex' instead of a 'byte[]', otherwise the same algorithm.
Or the table can be "0123456789ABCDEF" and the StringBuilder can append
charAt()s. No more specious exception, either.

static final String HEXES = "0123456789ABCDEF";
public static String getHex( byte [] raw )
{
if ( raw == null ) // or could just let throw NPE
{
return null;
}
final StringBuilder hex = new StringBuilder( 2 * raw.length );
for ( final byte b : raw )
{
hex.append( HEXES.charAt( (b & 0xF0) >> 4 )
.append( HEXES.charAt( (b & 0x0F) );
}
return hex.toString();
}

--
Lew
From: Lew on 29 Dec 2009 17:46
Lew wrote:
>>   static final String HEXES = "0123456789ABCDEF";
>>   public static String getHex( byte [] raw )
>>   {
>>     if ( raw == null ) // or could just let throw NPE
>>     {
>>       return null;
>>     }
>>     final StringBuilder hex = new StringBuilder( 2 * raw.length );
>>     for ( final byte b : raw )
>>     {
>>       hex.append( HEXES.charAt( (b & 0xF0) >> 4 )
>>          .append( HEXES.charAt( (b & 0x0F) );
>>     }
>>     return hex.toString();
>>   }
>

Real Gagnon wrote:
> Your suggestion about the usage of a StringBuilder to get rid of the
> exception declaration is a good one but your code has a 2 missing ")".
>
>       hex.append(HEXES.charAt((b & 0xF0) >> 4))
>          .append(HEXES.charAt((b & 0x0F)));
>

Oopsie.

That's the risk of posting code one hasn't compiled. When I do
occasionally compile code before posting, I enclose it in the (fake
XML) tag "<sscce>" or explicitly mention that I compiled the code
first, otherwise typos and bugs are left for the reader to discover.

Good catch.

--
Lew
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