question: public static byte [ ] decode ( String hexa ) throws CoderException { if ( hexa == null ) { throw new CoderException ( "can't decode empty String" ) ; } if ( ( hexa . length ( ) % 2 ) != 0 ) { throw new CoderException ( "invalid hexadicimal String" ) ; } int tamArray = hexa . length ( ) / 2 ; byte [ ] retorno = new byte [ tamArray ] ; for ( int i = 0 ; i < tamArray ; i ++ ) { retorno [ i ] = hexToByte ( hexa . substring ( i * 2 , i * 2 + 2 ) ) ; } return retorno ; }
target:  decodes back a String to a byte array