а что, не пойму.
package com.javarush.task.task19.task1925;
import java.io.*;
import java.util.ArrayList;
/*
Длинные слова
*/
public class Solution {
public static void main(String[] args) throws IOException {
String lineFromFile = "";
try (BufferedReader reader = new BufferedReader(new FileReader(args[0]));
FileWriter writer = new FileWriter(args[1])) {
while (reader.ready()) {
lineFromFile = lineFromFile + reader.readLine();
}
String[] data = lineFromFile.split(" ");
for (int i = 0 ; i < data.length ; i++) {
if (data[i].length() >= 6) {
writer.write(data[i]);
if (i < data.length-2) {
writer.write(",");
}
}
}
}
}
}