private void checkAndCreate() {		//checks validity of q20/txt file
		if(checkReader.hasNextLine()) {
			String firstLine = checkReader.nextLine();
			if(firstLine.equals("Q:") || firstLine.equals("A:")) {	//if first line is not Q or A, file is not valid
				checkReader.close();
				head = create(null, head);	//if file is valid, create tree
				return;
			}
		}
		checkReader.close();
		fReader.close();
		JOptionPane
				.showMessageDialog(
						null,
						"File is invalid. \nFind a valid .q20 file or a compatible text file.\nIf you can't find one, a read-only copy will be fetched from the internet.",
						"Error", JOptionPane.ERROR_MESSAGE);
		fileChoose();
	}