Этому валидатору "суперКлассЕгоЗаНогу"!
package com.javarush.task.task18.task1801;
import java.io.*;
/*
Максимальный байт
*/
public class Solution {
public static void main(String[] args) throws Exception {
try (BufferedReader reader = new BufferedReader(new InputStreamReader(System.in))) {
String fileName = reader.readLine();
Integer max = Integer.MIN_VALUE;
try (FileInputStream inputStream = new FileInputStream(fileName);
BufferedInputStream buffer = new BufferedInputStream(inputStream)) {
while (buffer.available() > 0) {
Integer c = buffer.read();
if (c > max) max = c;
}
}
System.out.println(max);
}
}
}