tasks2/KonwersjaLiter2/src/main/java/pl/dmcs/FileConverter.java

package pl.dmcs;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

public class FileConverter {

    public void convertToUpperCase(String filePath) throws IOException {
        Path originalPath = Paths.get(filePath);
        Path tempFilePath = Paths.get("target/test-classes/file.tmp");

        try (BufferedReader reader = new BufferedReader(new FileReader(originalPath.toFile()));
             BufferedWriter writer = new BufferedWriter(new FileWriter(tempFilePath.toFile()))) {

            reader.lines()
                    .map(String::toUpperCase)
                    .forEach(line -> {
                        try {
                            writer.write(line);
                            writer.newLine();
                        } catch (IOException e) {
                            throw new RuntimeException(e);
                        }
                    });
        }

        Files.delete(originalPath);
        Files.move(tempFilePath, originalPath);
    }
}