anyone please help me with this

Question about the task

Archiver (part 16)

Java Multithreading, Level 7, Lesson 15

Resolved

I've tried a bunch of methods but none are working

public void removeFiles(List<Path> pathList) throws Exception {
        if(!Files.notExists(zipFile))
            throw new NoSuchZipFileException();
        Path tempFile = Files.createTempFile(zipFile.getParent(),"tempFile",  ".zip");
        try (ZipInputStream zipInputStream = new ZipInputStream(Files.newInputStream(zipFile))){
            ZipEntry zipEntry = zipInputStream.getNextEntry();
            while (zipEntry != null) {
                if(pathList.contains(Paths.get(zipEntry.getName()))) {
                    ConsoleHelper.writeMessage("Removed this file " + zipEntry.getName());
                    continue;
                }
                else {
                    try (ZipOutputStream zipOutputStream = new ZipOutputStream(Files.newOutputStream(tempFile))) {
                        zipOutputStream.putNextEntry(new ZipEntry(zipEntry.getName()));
                        copyData(zipInputStream, zipOutputStream);
                        zipOutputStream.closeEntry();
                    }
                }
                zipEntry = zipInputStream.getNextEntry();
            }
            Files.move(tempFile, zipFile);
        }
    }

It's time to remove something from an archive. An archive is a tricky thing—you can't just go and remove an element.
Why? Imagine we decided to invent our own text compression algorithm. After examining the source text, we see that the phrase "being a programmer is cool" occurs often. In the second and subsequent instances of our phrase, we can replace the phrase with a note that this location represents the same phrase that was used in line S, starting from character K and N characters long. As we replace a lot of repeated phrases, the text shrink noticeably, but becomes unreadable to those not familiar with our compression algorithm.
Of course, we can recover the text (extract it). Now imagine what we need to remove the part of the text that is referenced by the compressed fragments. If we did this, our entire archive would become meaningless. That's why you can't simply remove part of an archive. This is a highly simplified description of a compression technique; in reality, everything is far more complicated.
As a result, to remove something from an archive, you need to create a new archive, and copy over everything except the removed file. Then you replace the old archive with the newly created one.

1. Add a public void removeFiles(List<Path> pathList) throws Exception method to the ZipFileManager class. It will remove files from an archive. A list of the relative paths to the files inside the archive will be passed in pathList.
It must:
1.1. Throw a NoSuchZipFileException if the archive file doesn't exist.
1.2. Create a temporary archive file in the default directory using the Files class's createTempFile() method.
1.3. Go through all the files of the original archive, and check whether the current file is in the list for removal.
- If the file is in the list, display a message indicating that we have removed the corresponding file and move on to the next file.
- If the file is not in the removal list, copy it to the new archive
1.4. Replace the original archive file with the temporary file we wrote all of the required files to. You need to do this using the Files class's move() method
2. Add a public void removeFile(Path path) throws Exception method to the ZipFileManager class. It should call the removeFiles method, creating a list out of a single element. This can be done using the Collections class's singletonList() method. Look up how it works.
3. Implement the ZipRemoveCommand class's execute() method: create a ZipFileManager object, ask the user which file to remove from which archive, and call the removeFile() method.
Do everything else as we did in the other commands. You don't have to catch the PathNotFoundException, since the removeFile() method shouldn't throw it.
4. Run the program and verify that removing a file from an archive works.

Requirements:

You need to create a public void removeFiles(List<Path> pathList) throws Exception method in the ZipFileManager class.
The removeFiles method must throw a NoSuchZipFileException if the archive file doesn't exist.
The removeFiles method must create a temporary archive file using the Files.createTempFile method.
The removeFiles method should write all of the files from the old archive to the new archive, except those in the list for removal.
In the ZipFileManager class, you need to create a public void removeFile(Path path) throws Exception method that delegates the call to the removeFiles(List<Path> pathList) method.
The ZipRemoveCommand class's execute() method should get the ZipFileManager object and remove from the archive the file read from the console.

package com.codegym.task.task31.task3110; import com.codegym.task.task31.task3110.exception.NoSuchZipFileException; import java.io.IOException; public class Archiver { public static void main(String[] args) throws IOException { Operation operation = null; do { try { operation = askOperation(); CommandExecutor.execute(operation); } catch (NoSuchZipFileException e) { ConsoleHelper.writeMessage("You didn't select an archive or you selected an invalid file."); } catch (Exception e) { ConsoleHelper.writeMessage("An error occurred. Please check the entered data."); } } while (operation != Operation.EXIT); } public static Operation askOperation() throws IOException { ConsoleHelper.writeMessage(""); ConsoleHelper.writeMessage("Select an operation:"); ConsoleHelper.writeMessage(String.format("\t %d - Zip files into an archive", Operation.CREATE.ordinal())); ConsoleHelper.writeMessage(String.format("\t %d - Add a file to an archive", Operation.ADD.ordinal())); ConsoleHelper.writeMessage(String.format("\t %d - Remove a file from an archive", Operation.REMOVE.ordinal())); ConsoleHelper.writeMessage(String.format("\t %d - Extract an archive", Operation.EXTRACT.ordinal())); ConsoleHelper.writeMessage(String.format("\t %d - View the contents of an archive", Operation.CONTENT.ordinal())); ConsoleHelper.writeMessage(String.format("\t %d - Exit", Operation.EXIT.ordinal())); return Operation.values()[ConsoleHelper.readInt()]; } }

Comments (5)

Popular
New
Old

You must be signed in to leave a comment

Niladri pradhan

Level 33 , Mumbai, India

11 December 2019, 10:30

How did you solve it then

Nithin

Level 35 , Hyderabad, India

30 July 2019, 06:46

Line 21 should be

Files.move(tempFile, zipFile, StandardCopyOption.REPLACE_EXISTING);

Niladri pradhan

Level 33 , Mumbai, India

11 December 2019, 10:30

It didn't solve the problem verification still failed

Seb

Level 41 , Crefeld, Germany

31 January 2020, 14:02

The continue statement on line 145 creates a problem and needs to be removed. That should solve the issue then.

Henrique

Level 41 , São Paulo, Brazil

13 August 2020, 18:24

Line 156, right?