Проблема с валидатором

package com.javarush.task.task18.task1819; /* Объединение файлов */ import java.io.*; public class Solution { public static void main(String[] args) throws IOException { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); String firstFile = reader.readLine(); String secondFile = reader.readLine(); FileInputStream inputStream1 = new FileInputStream(firstFile); byte[] massiv1 = new byte[inputStream1.available()]; while (inputStream1.available() > 0) inputStream1.read(massiv1); inputStream1.close(); FileInputStream inputStream2 = new FileInputStream(secondFile); byte[] massiv2 = new byte[inputStream2.available()]; while (inputStream2.available() > 0) inputStream2.read(massiv2); inputStream2.close(); reader.close(); byte[] massiv3 = new byte[inputStream1.available() + inputStream2.available()]; System.arraycopy(massiv2, 0 , massiv3, 0, massiv2.length); System.arraycopy(massiv1, 0, massiv3, massiv2.length, massiv1.length); FileOutputStream outputStream = new FileOutputStream(firstFile); outputStream.write(massiv3); outputStream.close(); } }