ObjectInputStream instance of

Question

I'm trying to read from a file I have saved using the following code:

    public void saveOnFile() {
    try {
        ObjectOutputStream output = new ObjectOutputStream(new FileOutputStream("object.txt"));
        output.writeObject(mediaList);
        output.close();
    } catch(Exception ex) {
        ex.printStackTrace();
    }
}

    public void readFromFile() {
    try {
        ObjectInputStream inStream = new ObjectInputStream(new FileInputStream("object.txt"));
        this.mediaList.add( (Media) inStream.readObject());
        inStream.close();
    } catch(Exception ex) {
        ex.printStackTrace();
    }
}

However, I don't know if ObjectInputStream knows what objects are inputted. Objects in this case can either be a "Movie" or a "TVShow" but the are all subclasses to Media.

I get the following errors:

java.lang.ClassCastException: java.util.ArrayList cannot be cast to project.Media
at project.MediaHandler.readFromFile(MediaHandler.java:66)
at project.Window.<init>(Window.java:73)
at project.Window.main(Window.java:199)

Answer 1

The Object that you wrote to the ObjectOutputStream is called mediaList, therefore I assume that this is an ArrayList<Media> rather than each individual Media object. On the ObjectInputStream, you are reading an object and casting it to Media, but I think that you will find that it is an ArrayList<Media> (or however mediaList is defined when it is written to the ObjectOutputStream).