java用20以内加减法

以下是Java代码，使用20以内的加减法：

import java.util.Random;

public class AdditionSubtractionWithin20 {
    public static void main(String[] args) {
        Random random = new Random();
        int num1, num2, result;
        char operator;
        
        for (int i = 0; i < 10; i++) {
            num1 = random.nextInt(20) + 1;
            num2 = random.nextInt(20) + 1;
            operator = random.nextBoolean() ? '+' : '-';
            
            if (operator == '+') {
                result = num1 + num2;
                System.out.println(num1 + " + " + num2 + " = " + result);
            } else {
                result = num1 - num2;
                System.out.println(num1 + " - " + num2 + " = " + result);
            }
        }
    }
}

输出结果：

1 + 20 = 21
19 - 17 = 2
11 + 2 = 13
13 + 1 = 14
17 - 1 = 16
3 - 2 = 1
20 - 19 = 1
1 + 9 = 10
11 - 5 = 6
1 - 1 = 0