Validate input of a scanner: is it an integer and within a certain number range?

问题

I'm new at programming and I am currently following a Java class where I must validate a user's scanner input. The code below seems to work but I think it's a little bit inefficient. There must be a better way to do this!

Your suggestions are welcome!

Here's what I've got:

do {
    System.out.println("What is you age?");
    while (!scSudoku.hasNextInt()) {
        System.out.println("You must enter an number");
        scSudoku.next();
    }
    age = scSudoku.nextInt();
    if (age < 10 || age > 90) {
        System.out.println("You age must be within 10 and 90");
    }
} while (age < 10 || age > 90);

回答1:

Use nextLine() to discard any bad input.

Prevent code-duplication by using a never-ending loop, and either break or return to exit the loop. I prefer isolating the code in a helper method and use return.

private static int promptAge(Scanner sc) {
    System.out.println("What is you age?");
    for (;;) {
        if (! sc.hasNextInt()) {
            System.out.println("You must enter an number");
        } else {
            int age = sc.nextInt();
            if (age >= 10 && age <= 90)
                return age;
            System.out.println("You age must be within 10 and 90");
        }
        sc.nextLine(); // discard (rest of) line of input
    }
}

回答2:

Try replacing scSudoku.next(); with scSudoku.nextLine. It might run a little smoother, but my Java is a little rusty. I remember using nextLine or nextln instead of just next, and the programs worked.

EDIT: Try replacing scSudoku.next(); with scSudoku.nextln. It appears that nextln is more widely used.

EDIT 2: Or just use nextWhateverYou'reUsing.

来源：https://stackoverflow.com/questions/34907581/validate-input-of-a-scanner-is-it-an-integer-and-within-a-certain-number-range