在for循环中循环执行else语句？

Question

In this script, the user must input 5 numbers separated by new lines. The purpose is to check whether the input is an integer or not, and if it isn't, then it should theoretically loop, asking the user to input a valid integer .

The first part works - if the user inputs a value which isn't an integer, it throws the error and asks them to input a valid integer. But if they enter an invalid integer again, it throws an exception, which I don't want it to do. I want it to loop the else statement until the input is an integer.

I tried embedding a while loop within the else statement but it started getting messy and I couldn't figure out how to work it. Any help would be appreciated.

import java.util.*; 
import java.util.concurrent.TimeUnit;
public class NumbersArray
{
    int[] numbers = new int[5]; // Defines new array string with length of 5 characters
    Scanner sc = new Scanner(System.in);
    int length = numbers.length; // Defines length int, calculates how many in numbers int

    public void inputToNumbers()
    {
        for(int i=0; i<length; i++) // Declares i as 0, while i less than length loop runs. Increments each time
        {
            System.out.println("Input five whole numbers, separated by new lines:" + " (" + (i+1) + "/5)");
            String inputtedNums; // Declares inputtedNums string
            inputtedNums = sc.nextLine(); // Inserts input
            if (inputtedNums.matches("[0-9]+")) // Checks if the input is numbers only
            {
                numbers[i] = Integer.parseInt(inputtedNums); // Parses string input into integer numbers
            }
            else
            {
                System.out.println("Error! You inputted an invalid number, try again." + " (" + (i+1) + "/5)");
                inputtedNums = sc.nextLine(); // Takes user input
                numbers[i] = Integer.parseInt(inputtedNums); // Parses string input into integer numberS        
            }
        }
    }

    public void printTheNumbers()
    {
        for(int x=0; x<length; x++)
        {
            System.out.println(numbers[x]);
        }
    }

    public static void main(String[] args)
    {
        NumbersArray na = new NumbersArray();
        na.inputToNumbers();
        na.printTheNumbers();
    }
}

Answer 1

I think this will work fine.

public void inputToNumbers()
    {
        for(int i=0; i<length; i++) // Declares i as 0, while i less than length loop runs. Increments each time
        {
            System.out.println("Input five whole numbers, separated by new lines:" + " (" + (i+1) + "/5)");
            String inputtedNums; // Declares inputtedNums string
            inputtedNums = sc.nextLine(); // Inserts input
            while (inputtedNums.matches("^-?[^\\d]+$")) // Checks if the input is not number 
            {
                System.out.println("Error! You inputted an invalid number, try again." + " (" + (i+1) + "/5)");
                inputtedNums = sc.nextLine();

            }
            numbers[i] = Integer.parseInt(inputtedNums);
            // Parses string input into integer numbers
        }
    }

My concern is that whether negative integers are allowed or not? I have included an optional negative number case. See working code here : https://ide.geeksforgeeks.org/fzy9sHCGtz

Regex Test : https://regex101.com/r/KKrpUu/1

Answer 2

To expand on my comment, you can simplify your code this way:

Create an other method just to read a number from the console input and you can then call it again until you get an actual number. This replaces looping with recursion

public void inputToNumbers()
{
    int[] numbers = new int[5];
    for(int i=0; i<numbers.length; i++) {
        System.out.println("Input five whole numbers, separated by new lines:" + " (" + (i+1) + "/5)");
        numbers[i] = readNextnumber();
    }
}

private int readNextnumber() {
    Scanner sc = new Scanner(System.in);
    String inputtedNum = sc.nextLine();
    if(!inputtedNum.matches("[0-9]+")) {
        System.out.println("Error! You inputted an invalid number, try again.");
        return readNextnumber();
    } else {
        return Integer.parseInt(inputtedNum);
    }
}

Answer 3

Courtesy of @Bentaye, I added the following to my else statement:

        else
        {
            while(!inputtedNums.matches("[0-9]+"))
            {
                System.out.println("Error! You inputted an invalid number, try again." + " (" + (i+1) + "/5)");
                inputtedNums = sc.nextLine(); // Takes user input
            }
            numbers[i] = Integer.parseInt(inputtedNums); // Parses string input into integer numberS        
        }

And this worked perfectly.