code: private static char b64encode(int b)
  	{
  		if (b >= 0 && b <= 25)
  		{
  			return (char) ('A' + b);
  		}
  
  		if (b >= 26 && b <= 51)
  		{
  			return (char) ('a' + b - 26);
  		}
  
  		if (b >= 52 && b <= 61)
  		{
  			return (char) ('0' + b - 52);
  		}
  
  		if (b == 62)
  		{
  			return '+';
  		}
  
  		if (b == 63)
  		{
  			return '/';
  		}
  
  		return '?';
  	}
docs: Encode a 6-bit quantity as a base64 character.
  
  @param b
  The 6-bit quantity. return The character.