How to loop a user input until integer is entered?

Question

I want to run an interactive program where a user is prompted to enter a number of students. If the user inputs a letter or other character besides a whole number, they should be asked again ("Enter the number of students: ")

I have the following code:

public int[] createArrays(Scanner s) {
    int size;
    System.out.print("Enter the number of students: ");
    size = s.nextInt();** 
    int scores[] = new int[size];
    System.out.println("Enter " + size + " scores:");
    for (int i = 0; i < size; i++) {
      scores[i]=getValidInt(s,"Score " + (i + 1) + ": ");
    }
    return scores;
}

How can I create a loop for this?

Does this answer your question? How to loop user input until an integer is inputted? — Vinay Hegde
– Vinay Hegde, Commented May 1, 2020 at 5:18
@Eva Klein, did you check this post stackoverflow.com/questions/25277286/… — JenilDave
– JenilDave, Commented May 1, 2020 at 5:19

Lê Hoàng Dững · Accepted Answer · 2020-05-01 05:24:28Z

1

Let's add a loop, take the value as String and check if it is a number:

String sizeString;
int size;
Scanner s = new Scanner(System.in);
do {
        System.out.print("Enter the number of students: ");
        sizeString = s.nextLine();

} while (!(sizeString.matches("[0-9]+") && sizeString.length() > 0));
size = Integer.parseInt(sizeString);

answered May 1, 2020 at 5:24

Lê Hoàng Dững

4915 silver badges10 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Bradley · Accepted Answer · 2020-05-01 06:05:57Z

1

Try catching the exception and handling it until you get the desired input.

int numberOfStudents;

while(true)
{
    try {
        System.out.print("Enter the number of student: ");
        numberOfStudents = Integer.parseInt(s.next());
        break;
    }
    catch(NumberFormatException e) {
        System.out.println("You have not entered an Integer!");
    }
}

//Then assign numberOfStudents to the score array
int scores[] = new int[numberOfStudents]

answered May 1, 2020 at 6:05

Bradley

3373 silver badges11 bronze badges

Comments

Sachin Kumar · Accepted Answer · 2020-05-01 05:33:07Z

0

try this

public int[] createArrays(Scanner s) {
    int size;
    System.out.print("Enter the number of students: ");

    while(true) {
        try {
              size = Integer.parseInt(s.nextLine());
              break;
        }catch (NumberFormatException e) {
            System.out.println();
            System.out.println("You have entered wrong number");
            System.out.print("Enter again the number of students: ");
            continue;
        }
    }

    int scores[] = new int[size];
    System.out.println("Enter " + size + " scores:");
    for (int i = 0; i < size; i++) {
      scores[i]=getValidInt(s,"Score " + (i + 1) + ": ");
    }
    return scores;
}

answered May 1, 2020 at 5:33

Sachin Kumar

1,16710 silver badges15 bronze badges

Comments

Dulantha Madushan · Accepted Answer · 2022-03-18 13:51:14Z

0

int no1 = 0;

Scanner scanner = new Scanner(System.in);

    while(true)
    {
        try {
            System.out.print("Number 1: ");
            no1 = Integer.parseInt(scanner.next());
            break;
        }
        catch(NumberFormatException e) {
            System.out.println("..You have not entered valid value!");
        }
    }

answered Mar 18, 2022 at 13:51

Dulantha Madushan

1

Collectives™ on Stack Overflow

How to loop a user input until integer is entered?

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related