Improved Error Handling

Here is a version of the program that deals with non-integers in the data without using Exceptions. The scan.hasNextInt() checks that the next token can be parsed as an int. If so, the true branch of the if scans and parses the token. Otherwise, the false branch scans the next token, but does not try to convert it to an int.

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

public class SumFileDataImproved 
{
  public static void main (String[] args) throws IOException 
  { 
    int num,sum = 0;
    Scanner scan = null, scanUser = null;
    String fileName;
    
    try 
    {
      scanUser = new Scanner( System.in );
      System.out.println("Input file name: ");
      fileName = scanUser.nextLine().trim();
      
      File file = new File( fileName ); // create a File object
      scan = new Scanner( file );      // connect a Scanner to the file

      while( scan.hasNext() )   // is there more data to process? 
      {
        if ( scan.hasNextInt() )
        {
          num = scan.nextInt();
          sum += num;  
        }
        else
        {
          System.err.println( "Bad input data: " + scan.next()  + " skipped.");
        }        
      }
      
      System.out.println("Sum = " + sum );
    }
    
    finally 
    {
      if ( scan != null ) scan.close();
    }
  }
}

Here is some poor data, contained in the file poorRobin.txt:

3 6 12 17
14 4 32

23 ten
19

Here is the output of the program

C:\JavaSource> javac SumFileDataImproved.java
C:\JavaSource> java SumFileDataImproved
Input file name:
poorRobin.txt
Bad input data: ten skipped.
Sum = 130