ถามโคดเรื่องการตั้งโจทเลขครับ ผมติดอีกตรงแนวคิดอ่ะครับ ไม่ทราบว่าพี่ๆพอจะมีวิธีแนะนำหรือป่าว

public class JavaProjectTest {

    public static void main(String[] args) {

        Function1 fn = new Function1();

        //System.out.println(fn.condition());
        for (int i = 1; i <= 10; i++) {
            System.out.println(i + ". " + fn.random_Question());

            for (int j = 'a'; j <= 'd'; j++) {
                if (j == 'a') {
                    System.out.println("  a. " + fn.cal());
                } else if (j == 'b') {
                    System.out.println("  b. " + fn.cal());
                } else if (j == 'c') {
                    System.out.println("  c. " + fn.cal());
                } else if (j == 'd') {
                    System.out.println("  d. " + fn.cal());
                }
            }
        }

    }
}

import java.util.Random;

public class Function1 {

    Random random = new Random();
    int num_random;
    int rn_op = -3;
    int x, y, result;
    String[] condition = {"+", "-", "*", "/"};

    public int random_Question() {
        num_random = random.nextInt(200) + 100;
        return num_random;
    }

    public int random_choice() {
        do {
            num_random = random.nextInt(100);
        } while (num_random == 0 && num_random == 1);
        {
        return num_random;
        }
    }

    public int random_Option() {
        num_random = random.nextInt(3) + rn_op;
        return num_random;
    }

    public String cal() {
        String c = null;

        for (String condition1 : condition) {
            c = condition[random.nextInt(condition.length)];
            c.toString();
        }

        switch (c) {
            case "+":
                return plus();
            case "-":
                return del();
            case "*":
                return multi();
            default:
                return divide();
        }

    }

    public String plus() {
        int x, y, result;
        do {
            x = random_choice();
            y = random_choice();
            result = x + y;
        } while (result == num_random);
        {
            return x + " + " + y + " = " + (num_random);
        }

    }

    public String del() {
        int x = random_choice();
        int y = random_choice();
        int result = x - y;
        while (result != num_random) {
            x = random_choice();
            y = random_choice();
            result = x - y;
        }
        return x + " - " + y + " = " + (num_random);

    }

    public String multi() {
        int x = random_choice();
        int y = random_choice();
        int result = x * y;
        while (result != num_random) {
            x = random_choice();
            y = random_choice();
            result = x * y;
        }
        return x + " * " + y + " = " + (num_random);

    }

    public String divide() {
        int x = random_choice();
        int y = random_choice();
        int result = x / y;
        while (result != num_random) {
            x = random_choice();
            y = random_choice();
            result = x + y;
        }
        return x + " / " + y + " = " + (num_random);

    }

}