Can't figure out the last requirement. Is it possible that it would be cause by empty directory?

It's time to refactor the ZipFileManager class. The createZip method has code that we're also going to need in the methods that will add files to or remove them from an archive, extract files, etc. We'll implement those methods later, but we can move the common code to separate methods now.
Additionally, the createZip method can only create an archive from a single file, but we would like to be able to zip an entire folder. We won't create a separate method for this, since you can pass both a directory and a regular file to the createZip(Path source) method.

Today's tasks:
1. Implement a private void addNewZipEntry(ZipOutputStream zipOutputStream, Path filePath, Path fileName) throws Exception method in the ZipFileManager class.
It must:
1.1. Create an InputStream for the file named fileName located in the filePath directory
1.2. Create a new ZipEntry, using fileName as the name after converting it to a String
1.3. Copy the data from the InputStream (from step 1.1) to the zipOutputStream parameter
1.4. Close the zip entry
1.5. Close the InputStream using try-with-resources
2. Replace part of the createZip method's code with a call to the addNewZipEntry method. Pass source.getParent() as the filePath parameter, and source.getFileName() as the filename.
3. Implement a private void copyData(InputStream in, OutputStream out) throws Exception method. It must read data from "in" and write to "out", until it reads through everything.
4. Replace part of the addNewZipEntry method's code with a call to the copyData method.
5. Let's return to createZip:
5.1. At the beginning of the method, check to see if the directory (zipFile.getParent()) where we will create zipFile exists; if not, then create it.
5.2. If source is a regular file (use Files.isRegularFile to check), then simply call addNewZipEntry.
5.3. If source is a directory (use Files.isDirectory to check), then:
5.3.1. Create a FileManager object, passing source to the constructor
5.3.2. Get a list of files from the file manager, and save them to the fileNames variable
5.3.3. Call addNewZipEntry(zipOutputStream, source, fileName) for each element of fileNames.
5.4. If source isn't a folder or a file, throw a PathNotFoundException.