Question

This is a UML class diagram using Java syntax for the members. It is a summary of the design. The full details will follow.
AccountNumber
private int[] digits
public AccountNumber(boolean random)
public String toString()
public static AccountNumber fromString(String number)
private int checksum()

This version uses UML syntax for the members.
AccountNumber
-digits : int[]
+AccountNumber(random : boolean)
+toString() : String
+fromString(number : String) : AccountNumber
-checksum() : int

Fields
private int[] digits

Constructors
public AccountNumber(boolean random)

Methods
public String toString()
public static AccountNumber fromString(String number)
private int checksum()

Implement AccountNumber.checksum() and the constructor and test it with a program that generates random, valid account numbers. Use a command line argument to specify how many numbers to generate, as follows:
$javaGenerate 2(2 lines)
24568231
13789425

Answer 1

import java.util.Arrays;

public class JavaApplication {

public static void main(String[] args) {
int count = Integer.parseInt(args[0]);
for (int i = 0; i < count; i++) {
AccountNumber account = new AccountNumber(true);
System.out.println(account.toString());

}

}
}

class AccountNumber {

private int[] digits = new int[8];

public AccountNumber(boolean random) {

if (random) {
for (int i = 0; i < digits.length; i++) {
digits[i] = (int) (Math.random() * 10);

}

}

}

public String toString() {
String result = "";
for (int i = 0; i < digits.length; i++) {
result = result + digits[i];
}
return result;
}

public void setDigits(int[] digits) {
this.digits = digits;
}

public static AccountNumber fromString(String number) {

int[] arr = new int[number.length()];
for (int i = 0; i < arr.length; i++) {
char digit = number.charAt(i);
arr[i] = Character.getNumericValue(digit);
}
AccountNumber account = new AccountNumber(false);
account.setDigits(arr);
return account;
}

private int checksum() {
int result = 0;
for (int i = 0; i < digits.length; i++) {
result = result + digits[i];
}
return result;
}
}