Normal syntax?

public class Solution {
    public static void main(String[] args) throws IOException {
        TreeSet<Character> treeSet = new TreeSet<>();
        String fileName = args[0];
        FileInputStream inputStream = new FileInputStream(fileName);
        int count = 0;
         while ((count = inputStream.read())!= -1) {
             boolean isChar = String.valueOf(Character.valueOf((char) count)).matches("[a-zA-Z]");
             if (isChar) {
                 String s = String.valueOf(Character.valueOf((char) (count))).toLowerCase(Locale.ROOT);
                 char[] chars = s.toCharArray();
                 for (char c : chars) {
                     treeSet.add(c);
                 }
             }
         }

         count = 0;
         for (Character character: treeSet) {
             System.out.print(character);
             count++;
             if (count >= 5){
                 break;
             }
         }



    }
}