Задача выполняется бесконечно
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 s1 = reader.readLine();
String s2 = reader.readLine();
reader.close();
FileInputStream fileInputStream = new FileInputStream(s1);
byte[] buffer1 = new byte[fileInputStream.available()];
while (fileInputStream.available() > 0){
fileInputStream.read(buffer1);
}
fileInputStream.close();
FileInputStream fileInputStream1 = new FileInputStream(s2);
byte[] buffer2 = new byte[fileInputStream.available()];
while (fileInputStream1.available() > 0){
fileInputStream1.read(buffer2);
}
fileInputStream1.close();
FileOutputStream fileOutputStream = new FileOutputStream(s1);
fileOutputStream.write(buffer2);
fileOutputStream.write(buffer1);
fileOutputStream.close();
}
}