Prompting for a positive integer and validating user input in Java I'm just starting out with Java, and trying to make a method to get a positive integer input from the console. My currently working implementation is this:

public static Scanner sc = new Scanner(System.in);

public static int getPositiveIntInput(String message) {

    int n;

    String error_message = "Error: input must be a positive integer.";

    System.out.print(message);
    while (true) { // This is often frowned upon?

        // Check that input is integer
        while (!sc.hasNextInt()) {

            System.out.print(error_message + "\n" + message); // Gets repeated
            sc.next();

        }

        n = sc.nextInt();
        sc.nextLine();

        // Check that input is positive
        if (n &gt; 0) {

            return n;

        } else {

            System.out.print(error_message + "\n" + message);

        }
    }

}


In order to make my code more readable and concise, I attempted to rid myself of the while (true) and several error message prints by combining the integer and positivity checks into one loop, but I'm not getting the behaviour I would expect:


public static int getPositiveIntInput(String message) {

    String error_message = "Error: input must be a positive integer.";

    System.out.print(message);

    // Check that input is integer and positive
    while (!sc.hasNextInt() || sc.nextInt() &lt;= 0) {

        System.out.print(error_message + "\n" + message);
        sc.next();

    }

    int n = sc.nextInt();
    sc.nextLine();

    return n;

}





What would be an effective way of improving the readability and reducing repetition while achieving the same functionality as in my original implementation? Particularly regarding the while(true) loop - I've seen it's use being discouraged in other SO threads. Would this be a case where a different looping structure could/should be considered?
while (true) { // This is often frowned upon?



Frowned upon? Not that I know of.

Using a scanner for extracting numbers or tokens from a stream of input is great when the data is guaranteed to be in the expected format, and when it's ok to crash on any error.

The .nextInt and similar methods are less practical when you have to validate the input and give a chance to retry. In such cases I find it a lot more practical to read line by line, and perform the integer parsing manually, like this:

public static int getPositiveIntInput(String message) {    
    System.out.print(message);

    while (true) {
        String line = sc.nextLine();
        try {
            int n = Integer.parseInt(line);
            if (n &gt; 0) {
                return n;
            }
        } catch (NumberFormatException e) {
            // ok to ignore: let it fall through to print error message and try next line
        }
        System.out.print("Error: input must be a positive integer.\n" + message);
    }
}