java - 循环执行3次

Question

我正在做一个学校练习，要求我修改 .java 代码，以便要求用户仅输入正确的数字 3 次。

我得到的代码是这样的:

    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++)

你知道我哪里出错了吗？

提前谢谢您!

Answer 1

只需添加一个从 0 开始的计数器，当它达到 3 时，就不再允许用户输入数字。每当用户写入非法内容时，计数器就加一。

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:此时这与您无关，但您的 valorNOk 非常多余。您可以简单地使用 break 来代替，如下所示:

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);
}

另外注意:即使用户输入错误3次，你仍然会打印“Data Correct...”。在 while 循环之后你可以做这样的事情:

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