Где ошибаюсь ?

package com.javarush.task.task18.task1816;

/*
Английские буквы
*/

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.regex.*;

public class Solution {
    public static void main(String[] args) throws FileNotFoundException, IOException {
        FileInputStream file = new FileInputStream(new File(args[0]));
        int count = 0;

        while (file.available()>0) {

            int b =  file.read();
            String let = Integer.toString(b);

            Pattern p =Pattern.compile("[a-zA-Z]");
            Matcher m =p.matcher(let);
            while (m.find()) {
                count++;
            }





        }
        file.close();
        System.out.println(count);
    }
}