java - 将 hasNextInt 与 do-while 循环一起使用，负整数不会出现错误消息

Question

我正在编写一个程序，其中包括测试用户输入是否为正整数，并在输入为非整数或负数时显示错误消息。如果输入非整数，我的代码会显示预期的错误消息，但如果输入负整数，则仅重新提示输入正整数。我尝试添加:

if (n <= 0);
System.out.print("You have not entered a positive integer"); 

之前

 n = input.nextInt();

但是即使输入正整数也会出现错误消息。

我也尝试过:

while (!input.hasNextInt() && n <= 0)

感谢任何帮助。

        Scanner input = new Scanner( System.in );
        int n = 0;

        do {
        System.out.print("Please enter a positive integer: ");
        while (!input.hasNextInt()){
            System.out.print("You have not entered a positive integer. \nPlease enter a positive integer: ");
            input.next();
        }
        n = input.nextInt();

        } while (n <= 0);

Answer 1

试试这个:

int n = -1;//<-- it won't allow user to skip the loop after first pass without proper input
do {
    System.out.print("Please enter a positive integer: ");
    try {
        n = input.nextInt();//<-- in one pass ask input from user only once
        if(0 > n) {
            System.out.print("You have not entered a positive integer. \nPlease enter a positive integer: ");
        }
    } catch (NumberFormatException ex) {
        System.out.println("Invalid number !");
        break;//<-- break loop here, if don't wana prompt user for next input
    } catch(java.util.InputMismatchException ex) {
        System.out.println("Oops number is required !");
        break;//<-- break loop here, if don't wana prompt user for next input
    }
} while (n <= 0);