Вроде потоки закрыл.
package com.javarush.task.task13.task1318;
import java.io.*;
import java.util.ArrayList;
import java.util.Scanner;
/*
Чтение файла
*/
public class Solution {
public static void main(String[] args) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
String filePath = reader.readLine();
InputStreamReader isr = new InputStreamReader(new FileInputStream(filePath));
int a;
ArrayList<Character> characterArrayList = new ArrayList<>();
while ((a = isr.read()) > 0) {
characterArrayList.add((char) a);
}
reader.close();
isr.close();
for (int i = 0; i < characterArrayList.size(); i++) {
System.out.print(characterArrayList.get(i));
}
}
}