Java，随机运算符；在方法中调用相同的方法

Question

我正在努力学习Java。我尝试解决一个小问题。此时我不知道该尝试什么了。我想生成 2 个随机数和 2 个随机运算符 (+/-)。如果这些结果在 0-20 之间，则打印一些内容，否则重新开始，直到结果在该范围内。调用方法时出现错误:randomQuestion();提前致谢!

import java.util.Random;
import java.util.Scanner;

public class ExercicesMathQuizz {
Random random = new Random();
private int randomQuestion(){

    //generate 2 random numbers 
    int number = random.nextInt(15)+1;
    int number2 = random.nextInt(15)+1;
    //initiate result 
    int res = 0;
    //operator
    String operator =  randomOperator();

    //if operator is "+" do sum
    //otherwise do subtraction
    if (operator.equals("+")) {
        res = num1+num2;
        return res;
    }
    //if(operator.equals("-")) {
    else {
        res = num1-num2;
        return res;
    }

}

private void checkResult() {
     int res = randomQuestion();
     //if the result is between 0 and 20 (inclusive)
            if (res > 0 && res <= 20) {
                System.out.println(res + " is between 0-20"); 
            }
            else {
                //start over again with new numbers
                randomQuestion();
            }

    //generate a random operator
    private String randomOperator() {
    return random.nextBoolean() ? "+" : "-";

  }
}

Answer 1

1)某些地方的变量名称错误。您将这两个数字初始化为 number 和 number2，但稍后在程序中调用 num1 和 num2 (我'我假设这些是相同的变量。

2) checkResult 方法后面缺少括号

3)您将所有方法设为私有(private)。根据您尝试执行的操作，这可能会导致问题。

4) 您永远不会从 randomQuestion 方法调用 checkResult()。由于无论 randomQuestion() 方法中有什么，它都会生成全新的结果，因此这是一个问题。我想让该方法接受一个整数，检查它是否有效，然后返回一个 boolean 变量。然后在randomQuestion()中您可以循环直到结果有效。检查下面的代码:

static Random random = new Random();
public void randomQuestion(){
    boolean valid = false;
    int res = 0;
    while(!valid) {
        //generate 2 random numbers 
        int number = random.nextInt(15)+1;
        int number2 = random.nextInt(15)+1;
        //initiate result 

        //operator
        String operator =  randomOperator();

        //if operator is "+" do sum
        //otherwise do subtraction
        if (operator.equals("+")) {
            res = number+number2;
            valid = checkResult(res);
        }
        //if(operator.equals("-")) {
        else {
            res = number-number2;
             valid = checkResult(res);

        }
    }
    System.out.println(res + " is between 1-20");
}

public boolean checkResult(int res) {
     //int res = randomQuestion();
     //if the result is between 0 and 20 (inclusive)
            if (res > 0 && res <= 20) {
                return true;
            }
            else {
                //start over again with new numbers
                return false;
            }
    }
    //generate a random operator
    private String randomOperator() {
        return random.nextBoolean() ? "+" : "-";
    }
  public static void main(String[] args) {
        Example example = new Example();
        example.randomQuestion();

  }