How to use Scanner to accept only valid int as input

Question

I'm trying to make a small program more robust and I need some help with that. ``` Scanner kb = new Scanner(System.in); int num1; int num2 = 0; System.out.print("Enter number 1: "); num1 = kb.nextInt(); while(num2 < num1) { System.out.print("Enter number 2: "); num2 = kb.nextInt(); } ``` Number 2 has to be greater than number 1 Also I want the program to automatically check and ignore if the user enters a character instead of a number. Because right now when a user enters for example `r` instead of a number the program just exits.

Accepted Answer

Use `Scanner.hasNextInt()`:

Returns `true` if the next token in this scanner's input can be interpreted as an `int` value in the default radix using the `nextInt()` method. The scanner does not advance past any input.

Here's a snippet to illustrate:

```
Scanner sc = new Scanner(System.in);
System.out.print("Enter number 1: ");
while (!sc.hasNextInt()) sc.next();
int num1 = sc.nextInt();
int num2;
System.out.print("Enter number 2: ");
do {
    while (!sc.hasNextInt()) sc.next();
    num2 = sc.nextInt();
} while (num2 < num1);
System.out.println(num1 + " " + num2);
```

You don't have to `parseInt` or worry about `NumberFormatException`. Note that since the `hasNextXXX` methods don't advance past any input, you may have to call `next()` if you want to skip past the "garbage", as shown above.

How to use Scanner to accept only valid int as input

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