Trying to read from text file

Question

I am trying to read the following from a text file:

12
650 64 1
16 1024 2

My attempt:

import java.util.Scanner;
import java.io.*;

class Test{

    public static void main(String[] args){
        String filnavn = "regneklynge.txt";
        Scanner innFil = null;
        try {
            File fil = new File(filnavn);
            innFil = new Scanner(fil);
            while (innFil.hasNextLine()) {
                String linje = innFil.nextLine(); 
                int tall = Integer.parseInt(linje);
                System.out.println(tall);
            }
        } catch(FileNotFoundException e) {
            System.out.println("Filen kunne ikke finnes");
        }
    }
}

The first number(12) Works fine, but then I get this

Exception in thread "main" java.lang.NumberFormatException: For input string: "650 64 1"

"it doesn't work" .. can you be a bit more specific about that part? — Stultuske, Jan 29 '18 at 12:35
The first version you posted, with `s.hasNext() ` instead of `innFil.nextLine()`, solved the problem you are asking about now. — Ole V.V., Jan 30 '18 at 05:51

score 1 · Answer 1 · answered Jan 29 '18 at 22:12

Suggestions:

You need two while loops, one nested inside of the other
the first one, the outer loop, you loop while (innFile.hasNextLine()) {...}
inside this loop you call String linje = innFile.nextLine(); once
Then create a 2nd Scanner object, Scanner lineScanner = new Scanner(linje);
and create a 2nd inner while loop that loops while (lineScanner.hasNextInt() {...}
inside of this loop, extract a single int via int tall = lineScanner.nextInt();
and put it into your ArrayList.
Be sure to call lineScanner.close(); after exiting the inner while loop and before exiting the outer loop.

score 0 · Answer 2 · answered Jan 29 '18 at 22:41

As long as you are reading the full line:

String linje = innFil.nextLine();

You can't treat them as an Integer because it's already a String

int tall = Integer.parseInt(linje);
// linje now has this = "650 64 1"

So that provokes the Exception: java.lang.NumberFormatException

Here is an approach to print the numbers:

import java.util.Scanner;
import java.io.*;

class Test{

    public static void main(String[] args){
        String filnavn = "regneklynge.txt";
        Scanner innFil = null;
        try {
            File fil = new File(filnavn);
            innFil = new Scanner(fil);
            while (innFil.hasNextLine()) {
                if (innFil.hasNextInt()) {
                    System.out.println(innFil.nextInt());
                } else {
                    innFil.next();
                }
            }
        } catch(FileNotFoundException e) {
            System.out.println("Filen kunne ikke finnes");
        }
    }
}

Trying to read from text file

2 Answers2