Question

I’d like to create a program wherein a user will type a number and the program will tell if it is divisible by 3 or not. But %, /, +, * can’t be used in the program. Anybody here got some ideas how to do that?

Answer 1

public static void main(String[] args) {
    String number = "123456";

    int sum = 0;
    for (char c : number.toCharArray()) {
        sum = sum - (0 - c) - '0';
        while (sum >= 3) {
            sum -= 3;
        }
    }
    System.out.print("divisible by 3? ");
    System.out.println(sum == 0);
}

Alternatively you can keep subtracting 3 until your number is either 0 (divisible by 3) or <0: not divisible by 3.

ps: it needs to be adapted if you want to deal with negative numbers