In Intelij everything works perfectly.
package pl.codegym.task.task18.task1819;
import java.io.*;
import java.util.Scanner;
public class Solution {
public static void main(String[] args) throws IOException{
Scanner scanner = new Scanner(System.in);
String fileName1 = scanner.nextLine();
String fileName2 = scanner.nextLine();
FileOutputStream fileoutputstream = new FileOutputStream(fileName1,true);
FileInputStream fileinputstream = new FileInputStream(fileName1);
FileInputStream fileinputstream2 = new FileInputStream(fileName2);
byte[]tablicaBajtowZPliku1 = new byte[fileinputstream.available()];
byte[]tablicaBajtowZPliku2 = new byte[fileinputstream2.available()];
byte[]tablicaBajtowZPliku2i1 = new byte[tablicaBajtowZPliku1.length + tablicaBajtowZPliku2.length];
if (fileinputstream2.available()>0)
tablicaBajtowZPliku2 = fileinputstream2.readAllBytes();
if (fileinputstream.available()>0)
tablicaBajtowZPliku1 = fileinputstream.readAllBytes();
PrintWriter printWriter = new PrintWriter(fileName1);
printWriter.print("");
printWriter.close();
fileoutputstream.write(tablicaBajtowZPliku2);
fileoutputstream.write(tablicaBajtowZPliku1);
fileinputstream.close();
fileinputstream2.close();
fileoutputstream.close();
}
}
