CodeGym/Help with Java Tasks/can you explain me how to resolve this task?

Level 23

Solec-Zdroj

13.03.2019
1779views
9comments

can you explain me how to resolve this task?

Question about the task

AmigoOutputStream

Java Core, Level 8, Lesson 8

Under discussion

need help

1 Change the AmigoOutputStream class so that it wraps the FileOutputStream class. Use inheritance.
2 When the close() method is called, perform the following sequence of actions:
2.1 Call the flush() method.
2.2 Append the following text "CodeGym © All rights reserved." Use the getBytes() method.
2.3 Close the stream using the close() method.

Requirements:

Don't change the main method.
The AmigoOutputStream class must inherit the FileOutputStream class.
The AmigoOutputStream class's constructor should accept a FileOutputStream object.
All write(), flush(), and close() methods in the AmigoOutputStream class must be delegated to the FileOutputStream object.
The close() method must first call the flush() method, append the additional text, and then close the stream.

package com.codegym.task.task18.task1813; import java.awt.*; import java.io.*; /* AmigoOutputStream */ public class AmigoOutputStream extends FileOutputStream{ public static String fileName = "C:/tmp/result.txt"; public FileOutputStream original; public AmigoOutputStream(FileOutputStream f) throws FileNotFoundException { super(fileName); this.original=f; } @Override public void close() throws IOException { FileOutputStream f = new FileOutputStream(fileName); while(true){ f.flush(); StringBuilder sb = new StringBuilder(); sb.append("CodeGym © All rights reserved."); String data = sb.toString(); InputStream is = new ByteArrayInputStream(data.getBytes()); System.setIn(is); } } public static void main(String[] args) throws FileNotFoundException { new AmigoOutputStream(new FileOutputStream(fileName)); } }

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Ulan Mukanbetov

Level 26 , Bishkek, Kyrgyzstan

10 September 2019, 11:03

Guadalupe Gagnon you are monster of Codegym! Thank you for advices and hints.

Guadalupe Gagnon

Level 37 , Tampa, United States

13 March 2019, 18:33

You are missing a lot of methods (all the write() methods and the flush() method). Also your close method is not supposed to create a new FileOutputStream object, you already have one saved as 'original'. Also, in the close method, do exactly what the requirements call for: original.flush(); original.write(the text to append); original.close();

Wojtek

Level 23 , Solec-Zdroj

13 March 2019, 18:40

thank you Guadalupe, can you also give me a links which are useful in learn wrappers? because i am not sure i understand it well :)

Wojtek

Level 23 , Solec-Zdroj

13 March 2019, 18:54

and what you ean text to append, in write method we can place byte or block of bytes so how to do in this case? maybe:

original.write(data.getBytes());

Guadalupe Gagnon

Level 37 , Tampa, United States

13 March 2019, 19:26

You can do this:

original.write("CodeGym © All rights reserved.".getBytes());

Guadalupe Gagnon

Level 37 , Tampa, United States

13 March 2019, 19:30

the rest of the methods just need to delegate the task to the variable for the FileOutputStream (original), for example, here is one of the methods that you do need with everything just delegated to the FOS variable:

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

to get a list of all the methods hit alt+insert and select "Override Methods.....". You only need to add all write(), flush(), and close() methods.

Nikolaos

Level 22 , Vrontados, Greece

20 January 2020, 17:11

Guadalupe Gagnon thank you!!!

Johannes

Level 27 , Centurion, Pretoria, South-Africa

9 April 2020, 06:15

Hi GUada. why ? Why do I need to use a method that I've never heard of until I now googled it ? "getBytes()" ? Surely original.write("CodeGym © All rights reserved.") is writing exactly what they want ? Any idea why the getBytes is necessary, or is it just to throw in a method without explanation ? thnks :)

Guadalupe Gagnon

Level 37 , Tampa, United States

9 April 2020, 13:16

Input and Output streams (File, ByteArray) don't work with Strings or chars, they work with bytes. When using them, without wrapping them up with a class that does, it is the programmers responsibility to convert to the bytes to and from Strings/chars.