Помогите разобраться, что я делаю не так.

public class Solution {
    public static void main(String[] args) throws Exception {
    BufferedReader reader = new BufferedReader(new InputStreamReader (System.in));
    String str = reader.readLine();
        ArrayList<Integer> mainList = new ArrayList<>();
        ArrayList<Integer> byteList1 = new ArrayList<>();
        ArrayList<Integer> byteList2 = new ArrayList<>();

    FileInputStream inputStream = new FileInputStream(str);

    while (inputStream.available() > 0){
        mainList.add(inputStream.read());
    }


    for (int x = 0; x < mainList.size(); x++){
        for (int i = 0; i < mainList.size(); i++){
            if (mainList.get(x).equals(mainList.get(i)))
                byteList1.add(mainList.get(i));
        }
        if (byteList1.size() > byteList2.size())
            byteList2 = byteList1;
            byteList1.clear();

    }
        inputStream.close();
        System.out.println(byteList2);
    }
}