Почему не пропускает валидатор, не пойму?
package com.javarush.task.task18.task1819;
/*
Объединение файлов
*/
import java.io.*;
import java.util.Arrays;
public class Solution {
public static void main(String[] args) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
String file1 = reader.readLine();
String file2 = reader.readLine();
FileInputStream fileInputStream = new FileInputStream(file1);
FileInputStream fileInputStream1 = new FileInputStream(file2);
int a = fileInputStream.available();
int b = fileInputStream1.available();
byte [] buffer1 = new byte[a];
byte [] buffer2 = new byte[b];
fileInputStream1.read(buffer1);
fileInputStream1.close();
fileInputStream.read(buffer2);
fileInputStream.close();
FileOutputStream fileOutputStream = new FileOutputStream(file1);
fileOutputStream.write(buffer1);
fileOutputStream.write(buffer2);
reader.close();
fileOutputStream.close();
}
}