Question

我正在进行学校练习，要求我修改.java代码，以便要求用户输入正确的数字仅 3次。

我得到的代码就是：

    public static void main (String[] args) {
        Scanner lector = new Scanner(System.in);
        int valorUsuari = 0;
        boolean valorNOk=true;
        while (valorNOk){
            System.out.print("Insert a number between 0 and 5: ");
            valorUsuari = lector.nextInt();
            lector.nextLine();
            if((valorUsuari >= 0)&&(valorUsuari <= 5)){
              valorNOk=false;    
            }
        }
        System.out.println("Data correct. You typed " + valorUsuari);
    }
}

我尝试在while条件之前执行此操作，但它似乎不起作用：

for (valorUsuari = 0; valorUsuari <= 3 ; valorUsuari++)

你知道我哪里出错吗？

提前谢谢！

Answer 1

只需添加一个从0开始的计数器，当它达到3时，不再允许用户输入数字。每次用户写入非法内容时，请向计数器添加一个。

public static void main (String[] args) {
    Scanner lector = new Scanner(System.in);
    int valorUsuari = 0;
    int counter = 0; //this is your counter, it starts at 0 because the user has failed 0 times at this point
    boolean valorNOk=true;
    while (valorNOk && counter < 3){
        System.out.print("Insert a number between 0 and 5: ");
        valorUsuari = lector.nextInt();
        lector.nextLine();
        if((valorUsuari >= 0)&&(valorUsuari <= 5)){
          valorNOk=false;    
        } else {
            counter++; //this is added to keep track of failed tries
        }
    }
    System.out.println("Data correct. You typed " + valorUsuari);
}

注意：此时此问题与您无关，但您的valorNOk非常多余。你可以简单地使用break代替：

public static void main (String[] args) {
    Scanner lector = new Scanner(System.in);
    int valorUsuari = 0;
    int counter = 0; //this is your counter, it starts at 0 because the user has failed 0 times at this point
    while (counter < 3){
        System.out.print("Insert a number between 0 and 5: ");
        valorUsuari = lector.nextInt();
        lector.nextLine();
        if((valorUsuari >= 0)&&(valorUsuari <= 5)){
            break; 
        } else {
            counter++; //this is added to keep track of failed tries
        }
    }
    System.out.println("Data correct. You typed " + valorUsuari);
}

另一个注意事项：即使用户错误地输入了三次，您仍然会打印"Data correct..."。在你的while循环之后，你可以做的是这样的事情：

if(counter < 3) {
    System.out.println("Data correct. You typed " + valorUsari);
} else {
    System.out.println("Too many tries. You are bad.");
}

Answer 2

稍微修改了一下，我使用了一个计数器int tries来跟踪尝试。

 public static void main(String[] args) throws Exception {
        Scanner lector = new Scanner(System.in);
        int valorUsuari = 0;
        boolean valorNOk = true;
        int tries = 0;
        while (valorNOk && tries < 3) {
            System.out.print("Insert a number between 0 and 5: ");
            valorUsuari = lector.nextInt();
            lector.nextLine();
           if ((valorUsuari >= 0) && (valorUsuari <= 5)) {
            valorNOk = false;
        } else {
            tries++;
        }
        System.out.println("Data correct. You typed " + valorUsuari);
    }

循环执行3次

2 个答案: