Проверял на 2 файлах, запись происходит, текст одинаковый
package com.javarush.task.task22.task2211;
import java.io.*;
import java.nio.charset.StandardCharsets;
/*
Смена кодировки
*/
public class Solution {
public static void main(String[] args) throws IOException {
}
private static void fileWork(String fileNameInput, String fileNameOutput) {
try (BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(fileNameInput), "Windows-1251"));
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(fileNameOutput), "UTF-8"))) {
while (reader.ready()) {
writer.write(reader.readLine());
}
} catch (IOException e) {
e.printStackTrace();
}
}
}