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Android Studio cannot read from file, does not exist

I'm trying to read from a file in Android Studio, in a small Java app. So I'm trying this:
File test = new File("C:\\testing\\testFile.dat");
if (test.exists()) {
System.out.println("test exists");
}
else {
System.out.println("test doesn't exist");
}
The file definitely exists, but it keeps on reporting that the file doesn't exist. I was able to work around this with another file by using the AssetManager and reading it through a stream, but the method I'm calling now requires a File's absolute path, but it's point blank refusing to find the file.
Am I doing something dumb, or misunderstanding something?
UPDATE
Ok, thanks for the input, I've now solved the problem. First I had to upload the file I wanted into the virtual device's storage, then I was able to get the path to it.
File test = new File(this.getFilesDir().getAbsolutePath(), "testFile.dat");

but the method I'm calling now requires a File's absolute path
Assets are files on your development machine. They are not files on the device.
Ideally, you switch to some library that supports InputStream or similar options, rather than requiring a filesystem path. If that is not an option, you can always get the InputStream from AssetManager and use that to make a copy of the data in some file that you control (e.g., in getCacheDir()). You can then pass the path to that file to this method.

You can place this file in your assets/ folder inside the android project and access using the following code.
val inputSteam = assets.open("testFile.dat")
or place it inside the res/raw folder and access it like below.
val inputStream = resources.openRawResource(R.raw.testFile)
We can't access a file on a development machine like this and won't be available on an android device so it will break so it's better if we move this somewhere inside the project and access it as above.

How close a file opened by java.awt.Desktop

How to close an opened excel file?
Open excel code is:
File file = new File("e:\\aaa.xlsx");
Desktop desktop = Desktop.getDesktop();
desktop.open(file);
What would be the close code?
just using java open and close Windows application like use mouse.

Forget it. Open here means that the registered application, Excel, takes over and opens a Window. After that you have no control, but watching. Excel will close.
File is a class that represents a file system path. Itself it has no state of associated reader/writer. Java 7 now parallel introduces a more evolved class Path. Besides (obviously) the path on the file system, it also stores what file system. With Path one can have more than one FileSystem, like a ZipFileSystem. That allows you to copy and rename files in a zip.
That was just an elaboration.

Can't find folder or file created with Android App with windows file exlorer

I'm creating a directory and a text file on the sdcard in one of my apps because I want to be able to move it to my computer for analysis. But I can't find the folder or the file I'm creating on my sdcard using the file browser on my computer.
I CAN find and read the file using my phones file manager but not using the file browser in windows.
So the file and folder are succesfully created and I can write to the file, I can also find and read the file using the file manager on my phone but I can't find either directory or file using my computer.
I have a uses permission for the application to allow it to write to external storage.
This is the code I use to create the file and directory.
String fileName = "testFil.txt";
String path = Environment.getExternalStorageDirectory().getAbsolutePath()+"/PulsApp";
File appDirectory = new File(path);
appDirectory.mkdirs();
File file = new File(path, fileName);
try {
file.createNewFile();
} catch (IOException e) {
}
Does anyone know what the problem is and how to fix it? I really need to be able to write files to my sdcard so I can transfer them to my computer.
I am completely baffled by this problem since all the research I've done point to that everyone else is doing the same thing.

If your device is running Android 3.0 or higher, you also need to use MediaScannerConnection to index your newly-created file before it will show up on a development PC's file explorer.
More accurately, the newly-created file needs to be indexed by the MediaStore. That will eventually happen for other reasons (e.g., device reboot). However, you are better served using scanFile() on MediaScannerConnection to get it to happen more quickly.
I blogged about this last summer.

Sometimes that the MediaScannerConnection will recognize the folder as a unknown type file, so try to create another folder inside the original one can avoid this problem.
I have met the same problem, and I use the method in the comment
And it works for me.

how to get the file and folder information in java?

I'm doing a project that has a module as "File or folder information". It means, I need all open files and open directory details.
E.g.:
If one file "aa.txt" was open by user, and the file is in "bb directory"; the output should be like
aa.txt that file be in open
bb dir be in open
and also, if you change that file, the message appear by that module as aa.txt that file has been modified by this user.

You won't be able to do that in pure java, you'll need to use a custom library (depending on the OS) as file/user/permissions information is hidden form Java to make it portable. You can only check if you can read or write to a file using standard java (you have few more methods as isDirectory, but not much more).

Please have a look at Java's java.io.File API. You will get most of the things there.
For checking if the file has been modified, you can use lastModified() method.
JDK 7 is giving a new The WatchService API and File Change Notification API. You can read about it here.

How can my Java program store files inside of its .jar file?

I know that .jar files are basically archives as well as being applications. What I'm asking is how can I store data(actual files not just strings) packed inside my program? I want to do this within my Java code.
The reason for this if your wondering is that I'm producing a server mod of a game. The server starts and creates all the level data and I want to store all these file inside my .jar app.

Yes you can do this.
Non-code resources in a JAR file on the classpath can be accessed using Class.getResourceAsStream(String). Applications routinely do this, for example, to embed internationalized messages as resource bundles.
To get your file into the JAR file (at project build time!), just copy it into the appropriate place in the input directory tree before you run the jar command. Build tools such as Maven, Gradle, etc can automate that for you.
Is there a way to add files to the archive within the app?
In theory, your application could store files inside its own JAR file, under certain circumstances:
The JAR has to be a file in the local file system; i.e. not a JAR that was fetched from a remote server.
The application has to have write access to the JAR file and its parent directory.
The application must not need to read back the file it wrote to the JAR in the current classloader; i.e. without exiting and restarting.
The JAR must not need to be be signed.
The procedure would be:
Locate the JAR file and open as a ZIP archive reader.
Create a ZIP archive writer to write a new version of JAR file.
Write the application's files to the writer.
Write all resources from the ZIP reader to the writer, excluding old versions of the applications files.
Close the reader and writer.
Rename the new version of the JAR to replace the old one.
The last step might not work if the initial JAR is locked by the JVM / OS. In that case, you need do the renaming in a wrapper script.
However, I think that most people would agree that this is a BAD IDEA. It is simpler and more robust to just write regular files.

The other answers have provided some good strategies, but I am going to suggest going in a somewhat different direction.
This game supposedly has graphics and is a desktop application. It is most easy to distribute desktop applications from a web server.
If both those things are true of your game, then look into using Java Web Start to deploy it.
JWS offers APIs not available to other apps. & one of particular interest to this problem is the PersistenceService. The PersistenceService allows for small amounts of data to be stored and restored by an app. (even when it is in a sand-box). I have made a small demo. of the PersistenceService.
The idea would be to check the PersistenceService for the application data, and if not found, use the data in the Jars. If the user/application alters the data, write the altered data to the PersistenceService.
JWS also offers other nice features like splash screens, desktop integration, automatic updates..

This is not possible. You however can look into embedded databases for your usecase. Java 6 comes with JavaDB. If you doesn't want to use it then you can find more here http://java-source.net/open-source/database-engines

I would recommend that you consider having two JARs: one to store your application's class files and another JAR to store the user data. If you do not have two separate JARs, then you will have difficulties obtaining a write lock from the Operating System (since you would be trying to overwrite the JAR containing your program while java is reading it).
To create a JAR, use the java.util.jar.JarFile class. There is also another question on stackoverflow which describes how to create/write a JAR file.

Don't do this. A jar file is a source of application classes and resources, not a file system. You wouldn't try to save files into a exe, would you?

By creating a file in the Source Packages (ex: /src/resource/file.txt) its contents can be read using Class.getResourceAsStream(String)
This is a working implementation of the following answer
InputStream is = Class.class.getResourceAsStream("/resource/file.txt");
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
StringBuilder sb = new StringBuilder();
String line;
while((line = br.readLine()) != null) {
sb.append(line).append("\n");
}
System.out.println(sb.toString());