В чем проблема? что забыл? На тесте проблем не обнаружил
package com.javarush.task.task19.task1910;
/*
Пунктуация
*/
import java.io.*;
public class Solution {
public static void main(String[] args) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
BufferedReader bRead = new BufferedReader(new FileReader(reader.readLine()));
BufferedWriter bWrite = new BufferedWriter(new FileWriter(reader.readLine()));
String txt = "";
while (bRead.ready()){
txt = txt.concat(String.valueOf((char)bRead.read()));
}
txt = txt.replaceAll("[^a-zA-Z0-9]+","");
bWrite.write(txt);
reader.close();
bRead.close();
bWrite.close();
}
}