Shift timestamps in SRT formatted subtitle files in a folder

SrtShifter.java

import java.io.BufferedWriter;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.time.LocalTime;
import java.time.format.DateTimeFormatter;
import java.time.temporal.ChronoUnit;
import java.util.Arrays;
import java.util.stream.Collectors;

public class SrtShifter {
    private static final String timestampsPattern = "^\\d+:\\d{2}:\\d{2},\\d{3} --> \\d+:\\d{2}:\\d{2},\\d{3}$";

    private static final DateTimeFormatter formatter = DateTimeFormatter.ofPattern("HH:mm:ss,SSS");

    public static void main(String[] args) throws IOException {
        if (args.length < 2) {
            System.out.println("Pass folder path and shift duration in milliseconds as arguments!");
            return;
        }

        System.out.println(Arrays.toString(args));

        String path = args[0];
        int shiftInMs = Integer.parseInt(args[1]);

        Files
                .list(Path.of(path))
                .peek(System.out::println)
                .filter(p -> p.toString().endsWith(".srt"))
                .forEach(srt -> {
                    try {
                        process(srt, shiftInMs);
                    } catch (IOException e) {
                        throw new RuntimeException(e);
                    }
                });
    }

    private static void process(Path srt, int shiftInMs) throws IOException {
        System.out.println("Processing " + srt.toAbsolutePath());

        BufferedWriter writer = Files.newBufferedWriter(
                Path.of(srt.getParent().toString(), "_" + srt.getFileName()), StandardOpenOption.WRITE, StandardOpenOption.CREATE
        );

        Files
                .readAllLines(srt, StandardCharsets.ISO_8859_1)
                .stream()
                .map(line -> {
                    if (!line.matches(timestampsPattern)) {
                        return line;
                    }

                    return Arrays
                            .stream(line.split(" --> "))
                            .map(s -> LocalTime.parse(s, formatter).plus(shiftInMs, ChronoUnit.MILLIS))
                            .map(lt -> lt.format(formatter))
                            .collect(Collectors.joining(" --> "));
                })
                .forEach(line -> {
                    try {
                        writer.write(line);
                        writer.newLine();
                    } catch (IOException e) {
                        throw new RuntimeException(e);
                    }
                });

        writer.close();
    }
}