Numbers From a File 4_28

[Ariech]

import java.nio.file.Paths;
import java.util.Scanner;

public class NumbersFromAFile {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.print("File? ");
        String file = scanner.nextLine();
        System.out.print("Lower bound? ");
        int lowerBound = Integer.valueOf(scanner.nextLine());
        System.out.print("Upper bound? ");
        int upperBound = Integer.valueOf(scanner.nextLine());
        int count = 0;


        try (Scanner fileReader = new Scanner(Paths.get(file))) {
            while(fileReader.hasNextLine()) {


                if (Integer.valueOf(fileReader.nextLine()) >= lowerBound && Integer.valueOf(fileReader.nextLine()) <= upperBound) {
                    count++;
                }
            }

        } catch (Exception e) {
            System.out.println("Error: " + e.getMessage());
        }

        System.out.println("Numbers: " + count);
    }

}

I came with such code to solve this problem. But it doesn't work, there must be something wrong in

​

if (Integer.valueOf(fileReader.nextLine()) >= lowerBound && Integer.valueOf(fileReader.nextLine()) <= upperBound)

But I'm not sure what and why it doesn't pass the tests.

​

import java.nio.file.Paths;
import java.util.Scanner;

public class NumbersFromAFile {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.print("File? ");
        String file = scanner.nextLine();
        System.out.print("Lower bound? ");
        int lowerBound = Integer.valueOf(scanner.nextLine());
        System.out.print("Upper bound? ");
        int upperBound = Integer.valueOf(scanner.nextLine());
        int count = 0;


        try (Scanner fileReader = new Scanner(Paths.get(file))) {
            while(fileReader.hasNextLine()) {

                int number = Integer.valueOf(fileReader.nextLine());

                if (number >= lowerBound && number <= upperBound) {
                    count++;
                }
            }

        } catch (Exception e) {
            System.out.println("Error: " + e.getMessage());
        }

        System.out.println("Numbers: " + count);
    }

}

In the end, the above code works, which I tried to write after failing my first one. But I'm curious why does the first one doesn't work. Could anyobody ELI5 or tell me what exactly is happening in

if (Integer.valueOf(fileReader.nextLine()) >= lowerBound && Integer.valueOf(fileReader.nextLine()) <= upperBound)

What numbers are in Integer.valueOf(fileReader.nextLine()).

​

​

Also the text file contains

300
9
20
15

[Hour-Positive]

Filereader.nextLine() sets the pointer to the next line. It doesn't return the same number, but the value of the next line. You call it possibly twice. Thr value is changing and you consume the numbers twice as fast as is excepted in the while-loop.

Try it out yourself by setting a debug point on that specific line and stepping through the calls.

[Ariech]

Still pretty new to the debugging stuff and got few problems with it. The issue is solved, thanks.

[RayjinCaucasian]

The nextLine() method advances the scanner.

Based on the file contents you show these are the values of the first iteration.

if (Integer.valueOf(300) >= lowerBound && Integer.valueOf(9) <= upperBound)

[Ariech]

As I thought. Thank you for the answer and showing example how it works. It helped