How to properly read integer from file in Java

Question

I have read previous posts and tryed to integrate code in to my project. I am trying to read integers from my txt file. I am using this method:

 static Object[] readFile(String fileName) throws FileNotFoundException {
    Scanner scanner = new Scanner(new File(fileName));
    List<Integer> tall = new ArrayList<Integer>();
    while (scanner.hasNextInt()) {
        tall.add(scanner.nextInt());
    }

    return tall.toArray();
}

I don't know the size of data, so i am using List in main calling method:

Object [] arr = readFile("C:\\02.txt");
System.out.println(arr.length);

I am getting that the array size is 0; The integers i am trying to read from the file is binary Sequence. (1010101010...) I thought that the problem is connected with scanner maybe he thinks that it is not the integer.

Answer 1

You can use BufferReader instead :

String line = "";
List<Integer> tall = new ArrayList<Integer>();
try {
    BufferedReader br = new BufferedReader(new FileReader(fileName));
    while ((line = br.readLine())!= null) {
        tall.add(Integer.parseInt(line, 2));
    }
    br.close();
}catch(IOException e) {}

Answer 2

If you are reading data in binary form then consider using nextInt or hasNextInt with radix.

while (scanner.hasNextInt(2)) {
    tall.add(scanner.nextInt(2));
}

Otherwise you will be reading integers as decimals so values may be out of integers range like in case of

11111111111111111111111111111111