1ое Переделанное

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.charset.StandardCharsets;
import java.nio.file.Path;
import java.nio.file.Paths;

public class BufferTask {
    public static void RefactorFile() throws IOException {
        Path inputFilePath = Paths.get("File.txt");
        Path outputFilePath = Paths.get("newFile.txt");

        try (FileChannel inputChannel = FileChannel.open(inputFilePath);
             FileChannel outputChannel = FileChannel.open(outputFilePath)) {

            ByteBuffer inputBuffer = ByteBuffer.allocate(1024);
            ByteBuffer outputBuffer = ByteBuffer.allocate(1024);

            while (inputChannel.read(inputBuffer) != -1 || inputBuffer.position() > 0) {
                inputBuffer.flip();

                StringBuilder modifiedData = new StringBuilder();
                while (inputBuffer.hasRemaining()) {
                    byte b = inputBuffer.get();
                    if (Character.isLetter(b) || b == ' ') {
                        modifiedData.append((char) b);
                    }
                }

                outputBuffer.clear();
                outputBuffer.put(modifiedData.toString().getBytes(StandardCharsets.UTF_8));
                outputBuffer.flip();

                while (outputBuffer.hasRemaining()) {
                    outputChannel.write(outputBuffer);
                }

                inputBuffer.compact();
            }
        }
    }

    public static void main(String[] args) {
        try {
            RefactorFile();
            System.out.println("Файл успешно преобразован.");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}