如何确保用户仅输入整数类型和大于0的整数？

Question

I am attempting to make sure the user input int type only and make sure the integer inputted is greater than 0 .

I was able to come up with the following to make sure the input is int type:

Scanner scan = new Scanner(System.in);
while(!scanner.hasNextInt()) 
{
    scanner.next();
}
int input = scan.nextInt();

But how should I include a condition checking to make sure the integer is greater than 0 as well?

Answer 1

The problem with your current approach is you've already ready the value from the Scanner before it reaches int input = scan.nextInt(); , meaning that by the time you use nextInt , there's nothing in the Scanner to be read and it will wait for the next input from user...

Instead, you could read the String from the Scanner using next , use Integer.parseInt to try and parse the result to an int and then check the result, for example...

Scanner scanner = new Scanner(System.in);
int intValue = -1;
do {
    System.out.print("Please enter a integer value greater than 0: ");
    String next = scanner.next();
    try {
        intValue = Integer.parseInt(next);
    } catch (NumberFormatException exp) {
    }
} while (intValue < 0);

System.out.println("You input " + intValue);

Answer 2

put an if statement inside your while loop like this

if(num <= 0){
   System.out.println("Enter a number greater than zero");
}
else{
   break;
}

Answer 3

You may use a condition in your code but not in the loop as. `

Scanner scan = new Scanner(System.in);
abc: 
while(!scanner.hasNextInt()) 
{
    scanner.next();
}
int input = scan.nextInt();
if(input <= 0){
   goto abc;
}

`

Answer 4

使用.isDigit（）方法，然后检查该数字是否大于0（如果是数字）