클래스

1)

public class Main {
    public static void main(String[] args) {
        Calculator cal = new Calculator();

        cal.add(1,6);
        System.out.println(cal.result);

        cal.sub(5,2);
        System.out.println(cal.result);

        cal.mul(5,7);
        System.out.println(cal.result);

        cal.div(10,2);
        System.out.println(cal.result);
    }
}

class Calculator{
    int result;

    public void add (int a, int b){
        result = a + b;
    }
    public void sub (int a, int b){
        result = a - b;
    }
    public void mul (int a, int b){
        result = a * b;
    }
    public void div (int a, int b){
        if(b!=0){
            result = a / b;
        }else {
            result = 0;
        }
    }

}