Removing the "app_" prefix when creating subdirectories in the internal storage of the application

Android provides many options for storing data permanently on the device. I chose internal storage , so please do not make suggestions for SD card storage. (I've seen too many questions about internal storage that have answers on SD cards!)

I would like to create subdirectories in the internal app store directory. I followed this SO answer reproduced below.

File mydir = context.getDir("mydir", Context.MODE_PRIVATE); //Creating an internal dir;
File fileWithinMyDir = new File(mydir, "myfile"); //Getting a file within the dir.
FileOutputStream out = new FileOutputStream(fileWithinMyDir); //Use the stream as usual to write into the file.

      

        
        
        
      

    

Unfortunately, this is the creation of subdirectories with the "app_" prefix. So from the example, the subdirectory looks like "app_mydir" (not ideal).

The answer to this SO question suggests that you can get rid of the "app_" prefix like this:

m_applicationDir = new File(this.getFilesDir() + "");
m_picturesDir = new File(m_applicationDir + "/mydir");

      

        
        
        
      

    

But I want to write a zip to something like /data/data/com.mypackages/files/mydir/the.zip.

So at the end, my code looks like this:

File appDir = new File(getApplicationContext().getFilesDir() + "");
File subDir = new File(appDir + "/subDir");
File outFile = new File(subDir, "/creative.zip");

      

        
        
        
      

    

But this creates another "File does not exist" error when I try this:

FileOutputStream fileStream = new FileOutputStream(outFile);

      

        
        
        
      

    

How can I (1) create a subdirectory without the "app_" prefix and (2) write a zip to it?

Also, if my first requirement is not sensible, tell me why in the comments! I'm sure the "app_" prefix has some meaning that eludes me.