#Salesforce #apex chunk of code which will #generate a #valid #acn for you, and can then generate a valid #abn from the acn as well.

abnAndAcnGenerator.java

@isTest
public class abnAndAcnGenerator {
    
    public class FailedToGenerateRandException extends Exception {}
    
    private static final Integer RAND_ATTEMPTS_LIMIT = 5;
    private static final List<Integer> ACN_WEIGHTS = new List<Integer>{8,7,6,5,4,3,2,1};
    private static final List<Integer> ABN_WEIGHTS = new List<Integer>{10,1,3,5,7,9,11,13,15,17,19};
    
    private static Set<String> acnCollisions = new Set<String>();

    public static String getRandACN() {
        Boolean gotMatch = false;
        Integer currAttempt = 1;

        while(!gotMatch && (currAttempt <= RAND_ATTEMPTS_LIMIT)) {
            currAttempt++;
            try {
                String candidate = genACN();
                if(!acnCollisions.contains(candidate)) {
                    acnCollisions.add(candidate);
                    return candidate;
                }
            }
            catch(Exception e) {
                continue;
            }
        }

        throw new FailedToGenerateRandException('Failed to get ACN: after ' + RAND_ATTEMPTS_LIMIT + ' attempts, could not generate an ACN that has not already been generated');
        return 'failed';
    }

    public static String genACN() {
        String ACN = '';
        Integer productSum = 0;

        //Generate the first 8 random integers, and sum the products of the integers and their corresponding weights
        for(Integer randIntIndex = 0; randIntIndex < 8; randIntIndex++) {
            Integer randNum = getRandIntLessThanTen();
            ACN += String.valueOf(randNum);
            productSum += (randNum * ACN_WEIGHTS[randIntIndex]);
        }

        //Join and return the check digit with the rest of the ACN
        Integer checkDigit = 10 - math.mod(productSum,10);
        return ACN + (checkDigit == 10 ? '0' : String.valueOf(checkDigit));
    }


    public static String getABNGivenACN(String ACN) {
        String ABN = '';
        Integer productSum = 0;

        //Extract the Integers from the ABN String, put them in the ABN string, and add to the productSum by multiplying
        // the elements by their corresponding ABN Weights, beginning from index 2 (as the ABN forms the last 9 digits of the ACN)
        for(Integer acnIntIndex = 0; acnIntIndex < 9; acnIntIndex++) {
            Integer currInt = Integer.valueOf(ACN.mid(acnIntIndex,1));
            ABN += String.valueOf(currInt);
            productSum += (currInt * ABN_WEIGHTS[acnIntIndex + 2]);
        }

        //Join and return the check digit
        Integer checkDigit = 89 - math.mod(productSum,89) + 10;
        return (checkDigit < 10 ? '0' + String.valueOf(checkDigit) : String.valueOf(checkDigit)) + ABN;
    }
    
    private static Integer getRandIntLessThanTen() {
        return Integer.valueOf(String.valueOf(math.random()).right(1));
    }
    
}