Вроде все копирует как надо, но проверку не проходит.
package com.javarush.task.task18.task1808;
/*
Разделение файла
*/
import java.io.*;
import java.util.ArrayList;
public class Solution {
public static void main(String[] args) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
String s1 = reader.readLine();
String s2 = reader.readLine();
String s3 = reader.readLine();
FileInputStream file1 = new FileInputStream(s1);
FileOutputStream file2 = new FileOutputStream(s2);
FileOutputStream file3 = new FileOutputStream(s3);
byte[] buffer = new byte[1000];
while (file1.available() > 0){
int count = file1.read(buffer);
int sum = count / 2;
if(count % 2 == 0) {
file2.write(buffer, 0, count / 2);
file3.write(buffer, sum, count);
}
else {
file2.write(buffer, 0, count - sum);
file3.write(buffer, sum + 1, count);
}
}
file1.close();
file2.close();
file3.close();
}
}