А передается какая-то стрелка вверх 
public class Solution {
    public static void main(String[] args) throws IOException {
        String fn1;
        String fn2;

        String[] nums = null;

        try(BufferedReader reader = new BufferedReader(new InputStreamReader(System.in))) {
            fn1 = reader.readLine();
            fn2 = reader.readLine();
        }

        try(BufferedReader fileReader = new BufferedReader(new FileReader(fn1))) {
            try(BufferedWriter fileWriter = new BufferedWriter(new FileWriter(fn2))) {
                while (fileReader.ready()) {
                    nums = fileReader.readLine().split(" ");

                    for (String n : nums) {
                        try {
                            fileWriter.write(Integer.parseInt(n));
                        } catch (NumberFormatException e) {}
                    }
                }
            }
        }
    }
}