?
package com.javarush.task.task18.task1819;
import java.io.*;
/*
Объединение файлов
*/
public class Solution {
public static void main(String[] args) throws Exception{
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
String filename1=reader.readLine(), filename2=reader.readLine();
FileInputStream fis1 = new FileInputStream(filename1), fis2 = new FileInputStream(filename2);
byte[] buf1 = new byte[fis1.available()];
byte[] buf2 = new byte[fis2.available()];
int count1 = fis1.read(buf1);
int count2 = fis2.read(buf2);
fis1.close();fis2.close();
FileOutputStream fos1 = new FileOutputStream(filename1,true);
fos1.write(buf2,0,count2);
fos1.write(buf1,0,count1);
fos1.close();
}
}