Java 循环直到用户输入值 0。值必须在 1-4 之间，如果超过 4，要求用户再次尝试输入

Question

I need to create a loop where the user can input any amount of numbers between 1-4 and then I calculate the average. Typing 0 will end the program and calculate the average. Any value greater than 4 or less than 0 should not count and ask the user to input the value again. I'm stuck on the last part. I'm not sure if the while loop is the correct loop to use either. Thanks for any help

public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    double sum = 0;
    double count = 0;

    while(input.hasNextInt()) {
        int num = input.nextInt();
        if (num == 0)
            break;
        if (num > 4)
            System.out.println("Invalid number");
        sum += num;
        count += 1;
    }

    System.out.println("Average: " + sum/count);
}

Answer 1

You will always hit the lines:

sum += num;
count += 1;

Because the code just drops through from the second if statement.

The following would work - note the else if and else blocks will only be executed when the first if drops through:

public static void main(String[] args) {

    Scanner input = new Scanner(System.in);
    double sum = 0;
    double count = 0;

    while(input.hasNextInt()) {
        int num = input.nextInt();

        if (num == 0) {
            break;
        }
        else if (num > 4) {
            System.out.println("Invalid number");
        }
        else {
            sum += num;
            count += 1;
        }
    }

    System.out.println("Average: " + sum/count);
}