如何跟踪FileOutputStream的下载量？

import java.io.FileOutputStream;
import java.io.IOException;

public class TrackedFileOutputStream extends FileOutputStream {
    private long bytesWritten;

    public TrackedFileOutputStream(String name) throws IOException {
        super(name);
        bytesWritten = 0;
    }

    @Override
    public void write(byte[] b) throws IOException {
        super.write(b);
        bytesWritten += b.length;
    }

    @Override
    public void write(byte[] b, int off, int len) throws IOException {
        super.write(b, off, len);
        bytesWritten += len;
    }

    @Override
    public void write(int b) throws IOException {
        super.write(b);
        bytesWritten++;
    }

    public long getBytesWritten() {
        return bytesWritten;
    }
}

public class Main {
    public static void main(String[] args) {
        try {
            TrackedFileOutputStream outputStream = new TrackedFileOutputStream("output.txt");
            outputStream.write("Hello, World!".getBytes());
            outputStream.close();

            long bytesWritten = outputStream.getBytesWritten();
            System.out.println("Bytes written: " + bytesWritten);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}