Task: IBAN





Java: import java.math.BigInteger;
import java.util.*;

public class IBAN {
    private static final String DEFSTRS = ""
            + "AL28 AD24 AT20 AZ28 BE16 BH22 BA20 BR29 BG22 "
            + "HR21 CY28 CZ24 DK18 DO28 EE20 FO18 FI18 FR27 GE22 DE22 GI23 "
            + "GL18 GT28 HU28 IS26 IE22 IL23 IT27 KZ20 KW30 LV21 LB28 LI21 "
            + "LT20 LU20 MK19 MT31 MR27 MU30 MC27 MD24 ME22 NL18 NO15 PK24 "
            + "PS29 PL28 PT25 RO24 SM27 SA24 RS22 SK24 SI19 ES24 SE24 CH21 "
            + "TN24 TR26 AE23 GB22 VG24 GR27 CR21";
    private static final Map<String, Integer> DEFINITIONS = new HashMap<>();

    static {
        for (String definition : DEFSTRS.split(" "))
            DEFINITIONS.put(definition.substring(0, 2), Integer.parseInt(definition.substring(2)));
    }

    public static void main(String[] args) {
        String[] ibans = {
                "GB82 WEST 1234 5698 7654 32",
                "GB82 TEST 1234 5698 7654 32",
                "GB81 WEST 1234 5698 7654 32",
                "SA03 8000 0000 6080 1016 7519",
                "CH93 0076 2011 6238 5295 7",
                "XX00 0000",
                "",
                "DE",
                "DE13 äöü_ 1234 1234 1234 12"};
        for (String iban : ibans)
            System.out.printf("%s is %s.%n", iban, validateIBAN(iban) ? "valid" : "not valid");
    }

    static boolean validateIBAN(String iban) {
        iban = iban.replaceAll("\\s", "").toUpperCase(Locale.ROOT);

        int len = iban.length();
        if (len < 4 || !iban.matches("[0-9A-Z]+") || DEFINITIONS.getOrDefault(iban.substring(0, 2), 0) != len)
            return false;

        iban = iban.substring(4) + iban.substring(0, 4);

        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < len; i++)
            sb.append(Character.digit(iban.charAt(i), 36));

        BigInteger bigInt = new BigInteger(sb.toString());

        return bigInt.mod(BigInteger.valueOf(97)).intValue() == 1;
    }
}






Fortran: program ibancheck

   use ISO_FORTRAN_ENV

   implicit none

   character(4), dimension(75) :: cc = (/ &
            "AD24","AE23","AL28","AT20","AZ28","BA20","BE16","BG22","BH22","BR29", &
            "BY28","CH21","CR22","CY28","CZ24","DE22","DK18","DO28","EE20","ES24", &
            "FI18","FO18","FR27","GB22","GE22","GI23","GL18","GR27","GT28","HR21", &
            "HU28","IE22","IL23","IQ23","IS26","IT27","JO30","KW30","KZ20","LB28", &
            "LC32","LI21","LT20","LU20","LV21","MC27","MD24","ME22","MK19","MR27", &
            "MT31","MU30","NL18","NO15","PK24","PL28","PS29","PT25","QA29","RO24", &
            "RS22","SA24","SC31","SE24","SI19","SK24","SM27","ST25","SV28","TL23", &
            "TN24","TR26","UA29","VG24","XK20" /)

    character(34), dimension(12) :: ibans = (/ "GB82 WEST 1234 5698 7654 32       ", &
                                               "GB82WEST12345698765432            ", & 
                                               "gb82 west 1234 5698 7654 32       ", &
                                               "GB82 TEST 1234 5698 7654 32       ", &
                                               "GR16 0110 1250 0000 0001 2300 695 ", &
                                               "GB29 NWBK 6016 1331 9268 19       ", &
                                               "SA03 8000 0000 6080 1016 7519     ", &
                                               "CH93 0076 2011 6238 5295 7        ", &
                                               "IL62 0108 0000 0009 9999 999      ", &
                                               "IL62-0108-0000-0009-9999-999      ", &
                                               "US12 3456 7890 0987 6543 210      ", &
                                               "GR16 0110 1250 0000 0001 2300 695X" /)

    integer :: i
    
    do i=1, size(ibans)
        if (checkIBAN(trim(ibans(i)))) then
            print *, "  valid IBAN: ", trim(ibans(i))
        else
            print *, "invalid IBAN: ", trim(ibans(i))
        end if
    end do

    return
 
contains

    function checkIBAN(ibancode) result(valid)
        character(len=*), intent(in) :: ibancode
        character(len=len(ibancode)) :: iban
        logical :: valid
        integer(int32) :: j, ascii, ibanSize 
        character(100) :: ibanRearrange, ibantoint
        character(2) :: temp
        valid = .false.

        iban = remove_blanks(ibancode)
        ibanSize = checkCountryCode(iban)
        if (ibanSize == len(trim(iban))) then
            ibanRearrange = iban(5:ibanSize)//iban(1:4)
            ibantoint = ""
            do j=1, ibanSize
                ascii = ichar(ibanRearrange(j:j))
                if ((ascii >= 65) .and. (ascii<=90)) then
                    write (temp,fmt='(I2)') ascii-55
                    ibantoint = trim(ibantoint) // temp
                else
                    ibantoint = trim(ibantoint) // ibanRearrange(j:j)
                end if 
            end do
            if (mod97(ibantoint) == 1) then
                valid = .true.
            end if
        end if
    end function checkIBAN
    
    function mod97(strint) result(res)
        character(len=*), intent(in) :: strint
        integer :: i, num, res
        res = 0
        do  i=1, len(trim(strint))
            read(strint(i:i),*) num
            res = mod((res*10 + num),97);
        end do
    end function mod97

    function checkCountryCode(iban) result(ibanlength)
        character(len=*), intent(in) :: iban
        integer(int16) :: ibanlength, i
        ibanlength = 0
        do i=1, size(cc)
            if (iban(1:2) == cc(i)(1:2)) then
                read(cc(i)(3:4),*) ibanlength
                exit
            end if
        end do
    end function checkCountryCode
 
    Recursive Function Stripper(string,ch) Result(stripped)
        Implicit None
        character(len=*), intent(in) :: string
        character, intent(in) :: ch
        character(:), allocatable :: stripped

        IF (LEN(string)==1) THEN
           IF (string==ch) THEN 
              stripped = ''
           ELSE
              stripped = string
           END IF
        ELSE
           IF (string(1:1)==ch) THEN
              stripped = stripper(string(2:),ch)
           ELSE
              stripped = string(1:1)//stripper(string(2:),ch)
           END IF
        END IF
    END Function stripper

    Function Remove_Blanks(string) Result(stripped)
        Implicit None
        character(len=*), intent(in) ::   string
        character(:), allocatable :: stripped

        stripped = trim(Stripper(trim(Stripper(string,' ')),achar(9)))
    END Function Remove_Blanks

end program ibancheck