ReadFile.java

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;
import java.io.*;
import java.util.*;

public class ReadFile {
    public static void main(String[] args) {
        try {
            String filePath = "input.txt";
            FileReader fileReader = new FileReader(filePath);
            BufferedReader bufferedReader = new BufferedReader(fileReader);
            String line;
            List<Integer> list = new ArrayList<>();

            while ((line = bufferedReader.readLine()) != null) {
                list.add(Integer.parseInt(line));
            }

            System.out.println("Original list: " + list);

            Collections.reverse(list);
            List<Integer> new_list = new ArrayList<>(list);

            System.out.println("Reversed list: " + new_list);
            bufferedReader.close();

            //  ask for output.txt
            String fileName = "output.txt";
            FileWriter fileWriter1 = new FileWriter(fileName);
            BufferedWriter bufferedWriter1 = new BufferedWriter(fileWriter1);

            for (Integer e : new_list) {
                bufferedWriter1.write(e.toString());
                bufferedWriter1.newLine();
            }

            bufferedWriter1.close();
            System.out.println("Reversed list written to " + fileName);

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}