Converting byte array to hex and back

public class HexUtil
{
  private static final byte[] hexalphabet = "0123456789ABCDEF".getBytes();
  public static String toHex( byte [] raw ) 
  {
    if ( raw == null )
      return null;
    StringBuilder hex = new StringBuilder( 2 * raw.length );
    for ( byte b : raw )
      hex.append(hexalphabet[(b & 0xF0) >> 4])
         .append(hexalphabet[(b & 0x0F)]);
    return hex.toString();
  }
}

public static byte[] fromHex(String s)
  {
    byte[] b = new byte[s.length() / 2];
    for (int i = 0, j=0; i < b.length; i++, j=i*2)
    b[i] = (byte) Integer.parseInt(s.substring(j, j + 2), 16);
      return b;
  }