Collect integers from a file - Java

There are a few problems with your code. As has been mentioned in the comments, you're not checking for array bounding and you're reading character by character. You may want to look into the BufferedReader class. It allows you to read an entire line in one go. You also may want to look into the parse() method of the various primitive types. The Number class has a parse method, and thus so do the Double, Integer, Long, Short, etc classes. Last, check out the java.util package. It has a lot of usefully collections such as lists, dictionaries (called Maps), and other things.

Here's some code that demonstrates all of the above to solve the problem you're having.

String line = null;
ArrayList<integer> numbers = new ArrayList<>();
//Try-with-resource, so the stream is automatically closed when we're done
try(BufferedReader reader = new BufferedReader(new FileReader("someFilePath"))){
    //While the last line we read is not null, aka EOF
    while((line = reader.readLine()) != null){
        //Split along spaces
        String[] ints = line.split(" ");
        //For each integer in the line
        for(String number : ints){
            try{
                //Try to parse the string into an integer
                Integer i = Integer.parse(number);
                //Add it to the list
                numbers.add(i);
            }
            catch(NumberFormatException ex){
                //Parsing failed, keep going anyway
                continue;
            }
        }
    }
}
catch(IOException ex){
    //TODO Handle exception
}