На примере всё отлично, не пойму что не так
package com.javarush.task.task19.task1925;
/*
Длинные слова
*/
import java.io.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Solution {
public static void main(String[] args) throws IOException {
if (args.length >=2) {
BufferedReader reader = new BufferedReader(new FileReader(args[0]));
BufferedWriter writer = new BufferedWriter(new FileWriter(args[1]));
StringBuilder sb = new StringBuilder();
while(reader.ready()) {
sb.append(reader.readLine());
}
reader.close();
Pattern p = Pattern.compile("(\\S{7,})", Pattern.MULTILINE);
Matcher m = p.matcher(sb.toString());
sb = new StringBuilder();
if (m.find()) {
sb.append(m.group(1));
}
while (m.find()) {
sb.append(",").append(m.group(1));
}
writer.write(sb.toString());
writer.flush();
writer.close();
}
}
}