Все работает, сбрасывать пытался тоже
package com.javarush.task.task19.task1925;
import java.io.*;
import java.util.ArrayList;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/*
Длинные слова
*/
public class Solution {
public static void main(String[] args) throws IOException {
String s1 = args[0];
String s2 = args[1];
BufferedReader reader = new BufferedReader(new FileReader(s1));
String line;
StringBuffer buffer = new StringBuffer();
while ((line = reader.readLine())!=null){
buffer.append(line).append(" ");
}
reader.close();
Pattern pattern = Pattern.compile("\\b\\w{7,}\\b", Pattern.UNICODE_CHARACTER_CLASS);
Matcher matcher = pattern.matcher(buffer);
FileWriter fileWriter = new FileWriter(s2);
BufferedWriter writer = new BufferedWriter(fileWriter);
ArrayList<String> list = new ArrayList<>();
while (matcher.find()) {
list.add(matcher.group());
}
String fin = String.join(",", list);
writer.write(fin);
writer.close();
}
}