question: static boolean checkStandardUPCEANChecksum ( CharSequence s ) throws FormatException { int length = s . length ( ) ; if ( length == 0 ) { return false ; } int sum = 0 ; for ( int i = length - 2 ; i >= 0 ; i -= 2 ) { int digit = ( int ) s . charAt ( i ) - ( int ) '0' ; if ( digit < 0 || digit > 9 ) { throw FormatException . getFormatInstance ( ) ; } sum += digit ; } sum *= 3 ; for ( int i = length - 1 ; i >= 0 ; i -= 2 ) { int digit = ( int ) s . charAt ( i ) - ( int ) '0' ; if ( digit < 0 || digit > 9 ) { throw FormatException . getFormatInstance ( ) ; } sum += digit ; } return sum % 10 == 0 ; }
target:  Computes the UPC/EAN checksum on a string of digits, and reports whether the checksum is correct or not.