How can I determine what I read from a file? Java

Question

So I want to read a file, that contains numbers separated by spaces. For example, the file "try.txt" content is:

1 2 3
4 5 6
7 8 9

I know how to read this numbers and store them in an array with a Scanner, and two nested for loops.Ignore any possible sintax errors here. It would look like:

int i,j;
Scanner sc
for(i=0;i<array.length;i++){
   for(j=0;j<array[i].length;j++){
      array[i][j]=sc.nextInt();
   }
}

So my question is, how can I check that what I am reading is actually an integer? What happens if nextInt() finds a letter, or another ASCII symbol?

Thank you.

This documentation from Oracle on [Scanner.nextInt()](https://docs.oracle.com/javase/8/docs/api/java/util/Scanner.html#nextInt--) might be useful. [Edit] your question if you have questions from there. Oracle is a major Java vendor so they provide good documentation. — Tom Blodget, Oct 06 '17 at 19:08

score 0 · Answer 1 · edited Oct 06 '17 at 18:32

0

Try this code

if (obj instanceof Integer) 
{
    // is a integer
} 
else 
{
   // is not
}

edited Oct 06 '17 at 18:32

Pritesh Patel

684
14
29

answered Oct 06 '17 at 18:01

Fernando Vicente

1
3

And what are you doing to get the `obj` in the first place? – Henry Oct 07 '17 at 08:26

score 0 · Accepted Answer · answered Oct 13 '17 at 12:35

At the end, I solved this problem using InputMissmatchException. Here is an example:

Scanner sc = new Scanner(System.in);
try{
    int a = sc.nextInt();
}catch(java.util.InputMismatchException e) {
        System.out.println("Invalid file content");
}

How can I determine what I read from a file? Java

2 Answers2