How to pass the validation

Im counting using Character.isAlphabetic with the same negative rasult as for Character.isLetter method. I have tested the solution. it counts only letters and results are ok. Why in cannot pass the validation?

import java.io.FileInputStream;

public class Solution {
    public static void main(String[] args) throws Exception{
        FileInputStream stream = new FileInputStream(args[0]);
        int count = 0;
        while (stream.available() > 0) {
            if (Character.isAlphabetic(stream.read())) count++;

        }

        stream.close();
        System.out.println(count);