Using Try/Catch Block to Identify Strings in File

Question

I am attempting to read a bunch of numbers from a file and add them up. But I have added a few Strings in the File also. I am now trying to read the numbers add them together and using the try/catch block I am trying to display an error when the file reads a string instead of a integer. However as soon as the code reads a string from the file it gives me the error, the code does not continue to add the numbers together. It simply prints the error and prints 0. How do I modify it so that it continues to read the numbers and add them together as well as display an Error message after it reads a string.

Code:

import java.io.File;
import java.io.FileNotFoundException;
import java.util.InputMismatchException;
import java.util.Scanner;
public class AddNumbers {

public static void main (String[]args) {
    try{
        File myFile = new File("numbers.txt");
        Scanner scan = new Scanner(myFile);

        int x;
        int y = 0;
        try{
            //Read file while it has a line 
            while(scan.hasNextLine()){
            //scan a integer value
                x = scan.nextInt();
            //Add the scanned value to y
                y = y+x;
            }
        }catch(InputMismatchException e){
            //If a string is found then print this error
            System.err.println("Strings found! Error!");
        }
        System.out.println(y);
        scan.close();

    }catch(FileNotFoundException e){
        System.err.println("No such file exists!");
        System.out.println();
    }


}

}

File Contents

Albert 
10000
20000
30000
Ben 
50000
12000
Charlie

just add the try-catch block inside the while instead of what you're doing — Typo, Jul 29 '15 at 18:59
Add a try catch around x = scan.nextInt(); so that the loop continues — Ryan, Jul 29 '15 at 18:59
Your answer can be found here: [Continue executing loop after catching an exception in try/catch](http://stackoverflow.com/questions/13805008/continue-executing-loop-after-catching-an-exception-in-try-catch) — CubeJockey, Jul 29 '15 at 19:00

score 1 · Answer 1 · answered Jul 29 '15 at 19:01

Firstly, the try-catch block is placed outside the while loop. In case an exception occurs, control reaches the catch block which prints the error message, and then exits the loop. You need to place the try-catch inside the loop.

Secondly, when Scanner#nextInt() throws an exception, the Scanner would not consume the input, causing an infinite loop in case an invalid integer is read. You can simply read the whole line using Scanner#nextLine() and parse it as an int:

while (scan.hasNextLine()) {
    try {
        // scan a integer value
        String line = scan.nextLine();
        x = Integer.parseInt(line);
        // Add the scanned value to y
        y = y + x;
    } catch (NumberFormatException e) { // this can be thrown by Integer.parseInt(line)
        // If a string is found then print this error
        System.err.println("Strings found! Error!");
    }
}

score 0 · Answer 2 · answered Jul 29 '15 at 19:01

0

Try reading the line as a string and then using Integer.parseInt(x) and catching that if it throws an exception.

See Here for information about Integer.parseInt()

answered Jul 29 '15 at 19:01

Jeremy W

1,889
6
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The question is about continuing the loop should an exception be thrown – CubeJockey Jul 29 '15 at 19:03

score 0 · Answer 3 · edited Jul 29 '15 at 19:29

0

You need to put the try/catch inside the while loop.

While(scan.hasNextLine()){
    try{
      x=scan.nextInt();
      // add
    }catch(InputMismatchException ime){
       //write error
    }
}

edited Jul 29 '15 at 19:29

Jeremy W

1,889
6
29
37

answered Jul 29 '15 at 19:04

vruum

455
1
5
14

Using Try/Catch Block to Identify Strings in File

3 Answers3