OK - quick question for everyone. I've solved the task - but when I tested the .close() method with a file of my own... it wrote the string to be appended TWICE I can't for the life of me figure out why... any ideas? 
package com.codegym.task.task18.task1813;

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

/*
AmigoOutputStream

*/

public class AmigoOutputStream extends FileOutputStream {
    public static String fileName = "[filename]";
    private FileOutputStream original;

    public AmigoOutputStream(FileOutputStream original) throws IOException {
        super(original.getFD());
        this.original = original;
    }

    @Override
    public void flush() throws IOException {
        original.flush();
    }

    @Override
    public void write(byte[] bytes) throws IOException {
        original.write(bytes);
    }

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

    @Override
    public void write (int b) throws IOException {
        original.write(b);
    }

    @Override
    public void close() throws IOException {
        original.flush();
        String toAppend = "CodeGym © All rights reserved.";
        write(toAppend.getBytes());
        original.close();
    }

    public static void main(String[] args) throws IOException {
        AmigoOutputStream amigoStream = new AmigoOutputStream(new FileOutputStream(fileName));
        amigoStream.close();
    }

}