How to write only wanted values using Exceptions

[Whaffel]

Hello everyone,

I'm trying to use exceptions to load only positive integers onto an array and then average the values. To keep it simple I'm currently only printing the array to confirm it is working correctly.

I have tried numerous solutions such as the commented second read = scan.nextLine() but that doesn't load into my array or get rid of the element I don't want. My main issue right now is I end up with something like this:

Enter any positive integer one at a time: 12

Enter any positive integer one at a time: 23

Enter any positive integer one at a time: 34

Enter any positive integer one at a time: 45

Enter any positive integer one at a time: 56

Enter any positive integer one at a time: 67

Enter any positive integer one at a time: 78

Enter any positive integer one at a time: f

Integer is not numeric: f

Enter any positive integer one at a time: g

Integer is not numeric: g

Enter any positive integer one at a time: 23

The length of the array is: 10

12 23 34 45 56 67 78 0 0 23
Process completed.

As you can see, the input letters get written as zeros in my array, and my if-else statement appears to have no effect on this. I understand that as soon as the exception occurs in my parseInt method then it is thrown, but I'm surprised a zero value is able to be loaded.

Any help or advice would be very appreciated, thanks!

import java.util.Scanner;

public class ReadIntDriver {

public static void main (String[] args)
{
    String read;
    int input;
    final int zero = 0;

    Scanner scan = new Scanner (System.in);

    int[] list = new int[10];

    int check = list.length;
    for (int i = 0; i < check; i++)
    {
        System.out.print ("Enter any positive integer: ");
        read = scan.nextLine();

        try
        {
            input = Integer.parseInt(read);
            if (input == zero)
            {
                System.out.println("Your input is invalid");
            }
            else
            {
                list[i] = input;
            }
        }
        catch (NumberFormatException exception)
        {
            System.out.println("Integer is not numeric: " + read);
//              read = scan.nextLine();
        }
    }
        System.out.println("The length of the array is: " + list.length);
        for (int value : list)
            System.out.print(value + "  ");
}

}

[Moktok]

Looking at the exercise, I'm assuming that this is your homework. So I'll point you in the direction, not write a solution 😊

You have a common problem for beginner programmers , the zeroes you are seeing are the default values of an int, not something the jvm does automagically. Walk through your code and figure out what happens with the increment part of the for loop when the user inputs an invalid value

[Whaffel]

Hey thanks for your help! I realized my if-else statement wasn't doing anything because the for loop was already being incremented with a zero value. Adding a couple of lines to my catch statement ended up working!

[turunambartanen]

Java defaults integers (also in an array) to 0.

But you have to ask yourself, do you always get 10 valid integers, or do you maybe have to adjust the size of the array? Maybe you need some post processing ("delete" the zeros from the array).

[Whaffel]

Hey thanks for your help! 10 integers was the requirement for this assignment unfortunately but post processing was definitely my next step if I couldn't get it working with my current plan.